Magnum head and exh manifold ID

Are you sure about that?

I have a set of stock LA covers and a set of stock magnum covers. The magnums have a full length baffle inside that reduces the inside volume of the valve cover by quite a bit. I do know for sure most roller rockers will interfer with the baffle on a stock magnum cover. I would think the LA cover would be roomier and have lees issues with interference with the rocker gear.

The only valve covers I have tried are the cast aluminum MP covers you see in pics of my engine and a set of Moroso chrome steel covers which also fit just fine.