For some reason teh passenger side valve gasket always leakes regardless of oem or not. My sister had hers replaced at the dealer, and I replaced mine at home after doing teh heads, and both passenger gaskets leak. When I pull mine I am going to use some sealant along the outer edge, the place they tend to leak.

More than tread lightly. Leave it like you were never there, nor anyone else.
'90 X-cab 4.88's 33 BFG AT's, rr ARB, Headers, Ignition upgrade, cold air induction.
'91 X-cab 5.29's 315's BFG MT's, rr ARB, custom bumper and flatbed