Here`s some info for you. I have done dozens of engine R&R over the years at work for customers who are replacing blown or otherwise damaged engines with similar used ones. If you expect to shop to source a good used engine/trans assembly and swap it in, assuming you find one willing to do so, will probably set you back $3-5k AT LEAST depending on what has to be done to the used mill. Around here a decent, used 350/350 combo purchased used will cost the shop $1500 or so and they will tack on a good $500 profit on that before even starting the job. Add in belts, hoses, gaskets, thermostat, exhaust with modifies trans crossmember, re-route or extend or fix things like fuel lines and wiring, plus labor and it will get very expensive, very quickly. And again that assumes you find a shop or garage willing to do the work. Every garage I`ve worked at systematicaly refused custom engine swaps because it allways comes out more expensive than the customer originally planned or has the money to pay for, and in the time it would take to do the shop can do untold brake/exhaust/suspension jobs and make 3X the profit. Not to rain on your parade but just being honest. The only type of shop that will probably consider doing this your local speed/race shop who does this on a daily basis. Again, expensive. And that`s assuming a good, running used engine/trans.
Where`s what I would do (and have done in the past) since you have a decent work space and good basic knowledge. If you want new/rebuilt, the best deal going as others have sais is a brand new GM crate engine. you can get a basic short block or a complete 350HO, ready to drop in, from $1500 to $3500 depending on options. These are brand new, not rebuilt and are warantied. A quick look at the jeg`s website and you can get a complete, ready to install 350 for $2200. A good, rebuilt transmission is around $1000-1300 depending on performance options and so forth. While not cheap, I think this is the best deal going for a new assembly, all you have to do is install it which you should be able to do.
If you want a good, used combo, then search the local classifieds for a decent running pick-up or express van. 88-93 will give you a centerbolt 350 with a non-copmuter controlled 700-r4 or 98-2000 a rollercam, vertec 350 and 4l65e. While these are basic tbi engines, you can keep the injection or swap an carb/intake on and have some fun with your regal. I`ve seen some of these locally in the 2500 to 3500 range. The bodies may be junk and rusted but who cares, you want the drivetrain. The advantage to this option is that while the drivetrain is used, you also get every accessory, part, wire and do-dad with the engine. Except for things like mounts which obviously wont fit, you get things like the starter, front accessory drive, exhaust manifolds and other small parts which nickle and dime the price of a swap with ease.
One other source for good used drivetrains is the auto auction. Most major citys have a place where used cars are aucitonned off between dealers where they purchase their lease returns for the used car lot. While these are abviously not good sources for older cars and trucks, the one here in Montreal has a second auction lot where older and wrecked cars are sold. That`s what you want. They frequently have what you`re looking for. 2 years ago I purchased complete 3rd gen z28 with a Lt1 and five speed for $600. It had been rear ended pretty bad but the the motor started and ran beautifully. It cost $150. to tow it back to my friends place where we proceded to pull the engine and trans and drop it into his 84 camaro. Total cost was about $1300 once all the other incidentals were included. It still runs like a charm. I have seen lots of trucks,
caprice copcars and other similar models roll through this auction and sell for less than $1200.
That`s what I would do (and have already done) for a inexpensive drivetrain swap. This won`t make your regal a race car but you`ll have more fun than with the v6 and gives you a good base for futur improvements.
Ok, rant finished, my $.04 given (too long a post for $.02)
deanlemans81