You shouldnt have any problems with the trans temp
with that cooler... move it over to the side and space
it off the radiator a couple of inches..I run a cooler
about the same size with out any radiator cooling, 5000
stall conv and OD with 4.10 gears.. at 75 mph I turn
2900 rpm and I have no issue with heat.. with the OD
and turning less rpm I have more slippage than you will
so dont worry about temp