Marc, I think you hit the nail on the head, I recall someone doing an engine swap to a later engine in an 86 and he said the valve covers hit the exhaust manifolds, he did a bit if grinding at the contact points on the manifolds and all was well.

Leo Paugh
It's not an attitude, it's just the way I am.
You are not forgotten
If things improve with age, I must be approaching magnificent. thumbs