Hello everyone.

I did a search and read most of the exhaust manifold posts but most of them were for identifying the manifolds someone already had. I need information about compatibility.

I started what I thought was a relatively straight-forward project and it snowballed on me. I tore apart my 66 this past weekend to go from headers back to manifolds. I had picked up a set of manifolds off ebay but unfortunately, they were very early 1965 manifolds and did not fit my 66. The collector on the passenger sides hits the frame and on the driver side it interferes with the canister oil filter.

I did find some period correct manifolds on ebay, but they were going for $500-$1000 per pair.

Since my car is not numbers matching or period correct, I am more interested in fitment and function than originality.

My question is: When GM redesigned the castings for exhaust manifolds in 1968, did they make them backwards compatible to fit the 66 and 67 frames?

Also, will mid-70's manifolds from police cars or trucks fit? Has anyone tried to put these later castings on a 66 or 67? The casting numbers for the police manifolds are: Right Hand side is #353030; Left hand side is #3994045

Anyone with experience or advise would be greatly appreciated. Thanks in advance for any help.

-Hoovestol