[DiGGM95]

I cant remember what gasket i used back when i put my new engine in, but im thinking i just used the larger thick gasket on the outer lip of the adaper, and the 2 hole gasket for the top, to help keep the bolts from seeping (maybe the o-ring is for early f-car lt1's, idk). Heres a link that shows a breakdown of the oil cooler and adapter: http://capricess.com/tech/oil_cooler/seo.htm

 

[DiGGM95]

I think i originaly tried putting both on at once, and iirc, the o-ring would squish out from around where the adapter lip met the block when tightened to 17 ft. lb. Btw, i know for a fact that the f car lt1 has a different style oil cooler adapter, and im pretty sure the o-ring is for them, idk.