Two versions of the Victor Pontiac are available for 389-455 competition engines. # ED2957 accepts standard flange carburettors and # ED2956 is for 4500 Series carbs. Both manifolds are ideal for drag racing (Super Stock, Super Gas, Super Comp, Brackets, etc.), marine or any application requiring maximum power up to 7500 rpm. Compatible with standard Pontiac cast iron heads, or use with Edelbrock Performer RPM Pontiac aluminium heads for maximum power. For best performance, use 1" Cloverleaf spacer # ED8718 with # ED2956. Port exit size at head is 2.10" x 1.08" with enough material to open it up to larger port openings. Made in USA