I wouldn't hesitate now to use a stock pan in your deal
I installed a tranny temperature gauge in my last street and strip pump gas car that I beat on the street and track with 10. inch high stall converter and later put a 9.0 inch T/A SS Hemi converter in the car with no other changes, the tranny temps never got above 220 F at the track when going rounds or on the street in the summer.
The motor made over 700 HP and more torque than HP, 3450 lbs. with me in it and it ran 10.00 at 134.+ MPH in the 1/4 mile
The tranny temp on the street were usually below 160 F, NOT GOOD
ATF needs to be at least 160 F or above for some of the additives in them to start working properly