I recently replaced the cylinder heads on my 1986 mercruiser 350 engine with a set from 1989 center bolt valve covers. The manifolds from the old heads fit my new heads but getting the sparkplugs in or out is real tight and the spark plug wire boot rubs against the manifolds. I noticed that the manifolds have notches in them but they don't line up with the spark plugs they did on the old heads thou.
