The 700R4 is the 1980's version of the 90's 4L60 trans, and the 4L60e is the newest electronic version of it.
A 700R4 used a Throttle Valve cable to get the proper pressures and shift points.
A newer 4L60e uses a computer to do all that.
The 4L80e is basically an updated computer controlled overdrive version of the TH400.
The billy badass.
I'm sure a beefed up 700R4 would do ya just fine if that's GROSS hp you're talking about.