This thread is right down my alley, so to speak.....
I would definitely go the way of the 200-4R and since I rebuilt mine and it's still running strong, I can tell you a couple of things that would help you out in the long run.
To find the best 200-4R, you need to look for the ones from the 86-88 Monte Carlo SS cars. They are more easier to obtain than the Buick Grand National trannies.
I purchased my crossmember from Chevy2only and picked it up at Carlisle Pa. some 4 yrs ago. I would highly recommend using the system from Bow Tie Overdrives for the TV cable set-up. It takes all the guess work out of mis-matching parts plus, it gives you some extra tuning abilities for your set-up.
Getting the torque convertor to lock-up was as simple as swapping out your brake light switch with a 86/88 Monte Carlo SS one. To have the lock-up function, you need 12v power source from the panel and have it thru the brake switch, ( with a fuseable link in that line ), and on to the lock up solenoid within the tranny.
http://static.summitracing.com/global/images/instructions/tci-376600.pdf
I am running 4.10 gears out back and when I fall into that overdrive gear, I am really cruzin.....