Not my own experience, just what I read here. Some have had fitment issues with early stock exhaust manifolds against late model heads. One member cracked a manifold before noticing the contact. Good luck with your build.
This is correct. Check for clearance with the original drivers side manifold. Check the manifold and the exhaust port on the head. Be careful grinding on the exhaust port as there is coolant under it. Not a fan of aluminum rocker arms on a street car, but I know people that run them. I'd run stock 273 rockers and shafts. An Isky E-4 is good but you can do better. The last one I bought, was a custom cam from Racer Brown. Stock pushrods should work fine. Sounds like it will be a really nice combination in a 4 speed car. Not sure if the original 65 manifold would be the best since you are running 66 up heads. What is the casting number on the intake?