[NMattison]

Hi Russ i have a 351w also mine had the 2 piece seal, which right now my machine shop is changing that. i had the rear main bored out to accept and circle seal. im not sure what year your block is but if its newer it may be a circle seal also. on mine it is a d4 block made in 74.if you need a two piece seal i can get you the part# of felpro racing gaskets. just email me if you need it. Neil