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"Spacers" would be needed to move the manifolds away from the block enough to clear the covers. We first tried manifold flanges (ordered from Speedway) as used by hot rodders when building exhaust headers. In the photo below, the 2 flanges are shown above 2 gaskets that came with the "rebuilders" set (by Fel Pro.)

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Although the 5/16" thick header flanges provided good spacing away from the block, the shape of the flange faces did not match the gaskets, nor the "flats" on the block. I tried a set of the Fel Pro gaskets NAPA usually provides for 351 heads, but they did not fits as well as the ones from the rebuilder. The rebuilder-provided gaskets -- Fel Pro from NAPA -- perfectly matched the flats on the block, but did not provide good overlap.

It was suggested that good spacers could be "water jetted" from 5/16" stock, so I had Lance at Haslag Steel use the "rebuilder's" gaskets as patterns, and cut two from 5/16" stock. I had NAPA order another set of Fel Pros like the ones from the engine rebuilder. The resulting spacers perfectly match the shape of 1) the gaskets, 2) the flats on the block and 3) the bolt holes.

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