A TH400 would be alot stronger that a 700R4 but no overdrive. 700R4's dont like alot of torque. I would go with a 200R4. They seem to hold up alot better and theres no electronics like in the 4L60 or the 4L80.

Oh yeah...Im on the 3rd "built" 700R4 in my GMC Syclone. Torque = Kaboom.

Joe K.

1963 Chevy Stepside
350 with 3 on the tree.
1960 Chevy Bel Air
35k original miles
1991 GMC Syclone #1557
1992 GMC Typhoon #0261