You know, I've read this entire thread and I have to say, "gee whiz," guys...
1. The 3.8 can be made to deliver decent horsepower, that's true, just go to turbobuick.com and you'll see. It's not huge money, either, if you use stock used parts that those guys are selling when they go nuts with their cars. I'm just saying...
2. The 3.8 will be the longest lasting platform (Buick V6) in production before too long. It's been around since 1962 in various forms and sizes and GM continues to use it. I wonder why??? Because it's a good design, pure and simple. Even just to rip off the carb the G-guys have and to put on junkyard fuel injection from a front drive mid-80's car will give you a nice jump up in driveability.
3. You don't automatically need to drop in a chevy small block for V8 excitement on a budget. Buick V8's do very well with stock bottom ends if you give them only mild oiling mods. These mods don't cost money as much as just time to smooth out some bores and enlarge some others. The highest price you pay is for a long 9/16" drill bit and a book that tells you how to do it. I find Buick 350 engines all day long for nothing - usually in the car - for just a couple of hundred bucks. It's mostly because it's not a chevy so most people are afraid.
I have run Buick 340 and 350 engines in G-bodies and it's awesome. The best part - all of your V6 accessories and pulleys go onto the front of the engine and the fuel lines hook up properly as well. You just need longer belts and radiator hoses from a 70's car with a 350 Buick and you are good to go.
The last car I picked up also had a good TH350 in it, which is a nice upgrade for the TH200 we have now... Until you put that 2004R in!
Whatever you do, just don't rule out a Buick small block swap until you do a little research...
Good luck on whatever you do!!