This is one of those deals where you could get a thread to 40 pages or more just talking about torque converters. There are so many variables, vehicle weight, power output of the engine, etc. Stall torque ratio is what benefits the drivetrain when looking at converters. Many STRs for stock converters is like 1.7-ish or so, I think, while many loose converters can vary from 1.8-2.5 or so, just depends on how it's built. Output engine toque x STR = transmission output torque. You can quickly see how you could blow street tires off easier with a higher stall.
Personally, I wouldn't see the need to go over 2800-3000 stall with a TH350/TH400 for the street on a mild build. Nobody stays long in their peak power band on the street if they even get there at all. That stall number is actually a tad variable anyway, since torque input would determine what it actually stalls at. In other words, put the same torque converter behind a big block and a heavier car, and it will have a slightly higher stall speed than if stuck behind a small block. Note too, that slippage=heat. So at some point, you can overdo it. A looser converter isn't a cureall for everything. But looser is mostly better- to a point. With your power, and you say you're probably not even making 400 lb/ft of torque, I'm thinking 3500 on the street is a bit too loose. I could be wrong. At any rate, if you add a stall converter, nothing wrong with adding a trans cooler as well. Can't hurt.
IMO, your major consideration is the cam. Notice when you have a clutch and manual transmission, you can just push in the clutch and idle all day with a huge cam profile. Not so much with an auto. That looser converter allows the lumpy cammed engine to keep running when sitting at a stop sign because you have a higher stall speed. Plus, it'll allow you to "band-aid" the lower end rpm with a tad more torque multiplication factor when starting from a stop, long before you even get into making good engine power. Sure, you'll use a teaspoon more fuel than normal driving around, but not much. The torque multiplication before you start to move is better all around with the looser converter anyway.
If you plan on stopping where you are with your build, and you want to just drive it around town, the 3000 stall is where I'd stop myself. Gives you room to bump up your engine power a bit in the future without having to get a new converter. You do what you want, as you're going to be driving it. The rear end will make some difference as well, although the deeper the gears, the less likely you'll need a high stall. Are you running a 3.42 or deeper gear? Or are you at 2.92 or 3.08, etc.? The taller, highway gears would benefit much more (bang for the buck) with a loose converter than deeper gears, but actually, all gears can benefit to a degree with a converter change. It's just not as much with deeper gearsets.
Drag race much? I'm no expert on drag racing because I haven't done it in years and I was a novice then, but the math says the looser converter means you'll be in your peak power band more often than on a stock stall, and a loosey goosey converter will help in that regard to a point. The dragstrip is where the high stall speeds shine in the slushboxes. You should (mathematically) get better times in both 60 foot and trap speeds if you just changed out a stock converter to a higher stall. Couple that with an adjustable suspension for optimal weight transfer and maybe some sticky tires, and you can pick up some real time real quick. I'll let the grizzled, long-term experience racers chime in on this, but I'm betting they'll tell you pretty much the same thing.
You don't need a wham-o-dyne $1500 race-only converter for the street. As just stated, any good, reliable brand off the shelf converter should do you just fine. It's another one of those deals where you need to identify what you want at the end (the goal), then combine the right parts to work together to get you there quickly and reliably.
Personally, I wouldn't see the need to go over 2800-3000 stall with a TH350/TH400 for the street on a mild build. Nobody stays long in their peak power band on the street if they even get there at all. That stall number is actually a tad variable anyway, since torque input would determine what it actually stalls at. In other words, put the same torque converter behind a big block and a heavier car, and it will have a slightly higher stall speed than if stuck behind a small block. Note too, that slippage=heat. So at some point, you can overdo it. A looser converter isn't a cureall for everything. But looser is mostly better- to a point. With your power, and you say you're probably not even making 400 lb/ft of torque, I'm thinking 3500 on the street is a bit too loose. I could be wrong. At any rate, if you add a stall converter, nothing wrong with adding a trans cooler as well. Can't hurt.
IMO, your major consideration is the cam. Notice when you have a clutch and manual transmission, you can just push in the clutch and idle all day with a huge cam profile. Not so much with an auto. That looser converter allows the lumpy cammed engine to keep running when sitting at a stop sign because you have a higher stall speed. Plus, it'll allow you to "band-aid" the lower end rpm with a tad more torque multiplication factor when starting from a stop, long before you even get into making good engine power. Sure, you'll use a teaspoon more fuel than normal driving around, but not much. The torque multiplication before you start to move is better all around with the looser converter anyway.
If you plan on stopping where you are with your build, and you want to just drive it around town, the 3000 stall is where I'd stop myself. Gives you room to bump up your engine power a bit in the future without having to get a new converter. You do what you want, as you're going to be driving it. The rear end will make some difference as well, although the deeper the gears, the less likely you'll need a high stall. Are you running a 3.42 or deeper gear? Or are you at 2.92 or 3.08, etc.? The taller, highway gears would benefit much more (bang for the buck) with a loose converter than deeper gears, but actually, all gears can benefit to a degree with a converter change. It's just not as much with deeper gearsets.
Drag race much? I'm no expert on drag racing because I haven't done it in years and I was a novice then, but the math says the looser converter means you'll be in your peak power band more often than on a stock stall, and a loosey goosey converter will help in that regard to a point. The dragstrip is where the high stall speeds shine in the slushboxes. You should (mathematically) get better times in both 60 foot and trap speeds if you just changed out a stock converter to a higher stall. Couple that with an adjustable suspension for optimal weight transfer and maybe some sticky tires, and you can pick up some real time real quick. I'll let the grizzled, long-term experience racers chime in on this, but I'm betting they'll tell you pretty much the same thing.
You don't need a wham-o-dyne $1500 race-only converter for the street. As just stated, any good, reliable brand off the shelf converter should do you just fine. It's another one of those deals where you need to identify what you want at the end (the goal), then combine the right parts to work together to get you there quickly and reliably.
