If you plumb the trans back into the rad, it raises the temp of your coolant somewhat when the trans reaches full operating temp. So, if you choose to do this, don't buy a cheap Howe rad, or go to a refurbished stocker,get a BeCool rated for your intended HP or more.

If you limit your system with the lack of a shroud or smaller size rad to fit a small block opening, or under drive pully's etc, you need to increase the effeciency of the rad to compensate. Same with plumbing it with a trans cooler. Its an added stress on the cooling system, so plan it all out ahead. Mine typically brings engine tempup from 175 to 185 on a hot day when the trans reaches temp...