Kurt, the L48 350/300 used in the '69 Corvettes (base engine) used the 3932386 (early), 3956618 (mid-year), and 3970010 (late) blocks, and all were 4-bolts. From then on, they used the 010 block for all 350 applications thru 1979, and starting in '71 the base versions were 2-bolts and the optional versions were 4-bolts.