Try using the "CD2 STOP OIL LEAK" stuff. It doesnt clog the seals and make the oil thick like most others it works to build up on the seals which have shrunk due to heat/ stress. Also its very clean ( clear liquid). Worked for me, but dont know how long it will last. I put the stuff in when I bought my car and have not leaked since ( I ran it once in the oil).

 

My Z28 doesnt leak oil after replacing intake gasket, oil cooler O ring, low oil sender, oil pan gasket, and all 3 front timing cover seals, that has been my leaks in the last 3 years, for now leak free Z, waiting for rear main and rear diff pinion seal to leak. The T/A has been easier to deal with as far as oil leaks go, just intake gasket and low oil sender.