Oil leak under high pressure?

After pulling the car out of winter storage, my Dart is now leaking oil? angry9: A lot of it... but only under high pressure. Another word, noting at idle, but when I rev the motor and get the oil pressure over 85 PSI, then it just start dripping like hell where the oil pan meets the block toward the tranny. The motor is a rebuild 440 with less then 10k miles on it. It does have a hi vol/hi press oil pump in it, a windage tray and a mod 699 pan. My guess is the rear main seal. :-( Any advise?