A vs LA 318's

Hello to all,

I have a 1966 Chris-Craft cabin cruiser with two 318's, Marine version. One of them burned a piston so I was going to get two rebuilt long blocks and swap them out. But here's the question. Since this boat was built in 1966, I assume the engines to be 1965's or possibly very early 1966. I believe that means they are Chrysler's original "A" type blocks with the poly heads. The rebuilt long blocks available are the "LA" type and I believe they have the wedge heads.

What I am concerned about is bolting up the wet exhaust manifolds to wedge type heads. I have read on this forum that the LA engine was 5 inches narrower measured at the outside of the valve covers. My fear is there will be a big difference in the location of the exhaust surface plane and compared to an A type with the Poly heads. Could someone please confirm this?

Assuming the wedge heads are not going to work in this marine application, would it be possible to purchase short blocks and re-condition the poly heads I have? Will they work on an LA 318 block?

Thanks so much in advance.