i have a 91 chevy truck with a 5.7, i removed the vortec type heads and installed a set of 882 heads and manifold. problem is that i have a oil leak at the back of the manifold. removed the manifold twice and resealed it, but no luck. does anybody know if there is a special gasket set for this swap. i tried not using the seals and just used sealant, but no luck. help.............!