180° is the normal operating temp for the transmission. Any prolonged running above that temp, the ATF starts to break down. Running on the torque converter only, unlocked, will bring temps up realll quick while towing. A stock, loose, converter doesnt help this situation. A lockup switch can help here, but ya gotta be real careful, at least initially (as you get used to it), so you dont burn up your stock lockup clutch.
If you have any doubts, add in an aftermarket cooler on the front of the rad. You would want to cut it into the hot outlet of the transmission, before the liquid cooler. Changing the fluid couldnt hurt either. .
As mentioned above, 1250-1300 egt's are acceptable for long periods.
good luck
-j