Greg, the absolute best option is to use an Extreme Automatics built 200R4 with bolt on bellhousing, and if you are drag racing it only, skip the lock-up torque converter. It's heavier.
You will have to use a US Cartool crossmember to fit it, but the floor remains uncut. Bolts right on otherwise.
I have the Stage 2 with a Precision of New Hampton 3800 stall with 3 carbon fiber lock-up clutch converter. It's the best automatic I ever drove and is essentially a 5 speed auto with the lock-up. I run 3.91 rear end gears and an injected 408 Magnum. It's quick, fast and ultra reliable.