I KNOW THE RUNNERS ARE DIFFRENT BECAUSE OF THE COLD START INJECTOR BUT IS THE BASE THE SAME

 

I dont know about the runners but the base is different because of the cold start injector. The later mainfolds, '90 - '92 I think, have the boss for the injector but it's not drilled....that's about it.

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'82 TA "FRANKENBIRD" - built with various F-Body parts from '82 to '96.
CURRENT: '91 305, '96 T-56 6 speed, 3.42 POSI, '89 WS6, '86 TPI, SLP 1 3/4" headers
SOON: 350, Trick Flow TW heads, GM-HOT cam kit, PBR disc

 

87 and later intakes used the revised center bolt angle, also the vette intake has no provision for egr crossover the exhaust gasses enter intake on a raised boss by the distributer hole.The 89 manifolds eliminated the cold start passage.