Need some purchasing advice

Hey there -
You asked for thoughts on the best OD tranny. Check out the threads on FABO regarding using a GM 200-4R trans behind a small block Mopar.
That's what I'm using. It fits an A-body trans tunnel without surgery to the tunnel and provides both a better gear spread and OD ratio than a Mopar OD trans.
I'll be using 4.30 gears in my '69 Dart and the 0.67 OD in the 200-4R will be like having 2.88 gears while in OD.