I have a 326 in my 67. It is the original motor for the car so I wanted to keep it. I had it bored .030 over and put a 068 cam in along with the usual 3 angle valve job etc. I found an original 4 barrel manifold and used a carter afb carb. I gasket matched the intake and exhaust ports and just used the stock log manifolds after deburing and matching them to the gaskets. That was almost 20yrs. ago and she still runs great. If I didn't have the original motor though I would go for the 400.