i have an intake gasket to which my heads were ported. i cannot id this gasket. it is copper cored, sandwiched between semihard black plastic. the only stampings on this gasket are "this side up" "fss" "gm".

the ports are 1.25" x 2.25". i have purchased felpro 1284, but the locator tabs dont even line up, let alone poor port placement. am i being confused by an LT1/4 difference? the heads are ported LT4.

any help is appreciated, thanks

jb