The 700R4 will hold up fine.....it appears the 700R4 gets a bad rap. maybe because if the TV cable is not adjusted correctly the trans will not last long. The 3/4 clutches will be the first to go. But this is the way the 700R4 was designed to work with the TV cable, before the release of the 4L60E.
I have a 700R4 behind a 425 hp 383, (700R4 in all three of my blazers) its been in my 1972 c10 for 2 years without any issues....maybe I am lucky because I rebuild transmissions and know how to make them last...
