[The Fixer]

I'd recommend a built 200-4R. GN's and T-types are running them into the low 10s, so if they're built right, they'll handle your 350 hp motor. It'll pretty much bolt in, except for the crossmember (pretty sure the trannys are the same length). You can get a non-lockup converter so you won't have to worry about a harness for that. Your car will definitely be quicker, and more fun to drive too, plus you'll get way better mileage on the highway having the OD with the 3.90s out back.