Hp manifolds

So you mark it off,remove the column and then cut the collar? How close to the firewall do you go?

Only you can answer that as each car is a little different. You'll need the engine installed and have the manifold on hand to make that determination. I have seen though that about one half to one inch of the column protruding from the firewall work in the few instances I have seen it done and the one time I did it myself.