Designed for street 262-400 c.i.d. Chevy V8s that have heads with canted center bolt holes. Both accept late-model water neck, air-conditioning, alternator, H.E.I. and have rear water crossovers. #2104 accepts exhaust-heated chokes. For 1987-95 stock aluminum heads use #2101. Will not fit Chevrolet Bowtie or LT1 heads.