The blinking of the O/D light indicates that theres a problem w/ the ECT(Elect. Controlled Trans).Check the trouble code first before anything else.Make it sure that a Toyota certified technician or a qualified engine tech/tuner from a reputable shop will diagnose your car.
With our 1997 Corona before:
1. Temp gauge never reached the halfway mark
2. We also followed the ATF specs on the dipstick before (when we did a full ATF dialysis).
3. Better to have a diagnostic scan on the AT blinking lamp. Do you feel any problems with the transmission (erratic shifting, strong shift shock, delays in gear engagement)?