Many years ago, a friend of mine had an Aussie delivered '68 Impala.
He fitted a Corvette 427 (with tri power) into it and found that the exhaust manifold on the driver side fouled the steering column - but not by much.
He was able to machine the manifold on the mating surface to the head on a slight angle to make the manifold more block hugging and clear the steering column.
As far as extractors are concerned, I reckon Chris is on the money with HQ idea.