My distributer is not seating all the way flush with the intake manifold on my 77 350. It looks like it needs to go down maybe 3/32 of an inch. I have no idea how many times the block was machined. I bought it from the machine shop. I was wondering if i needed to shim it due to block decking and the size of the combustion chambers. I just dont know how to go about this or what size shim I should use.