My suggestion is to put that 80 pounder on see how it fits.
It sounds like the Street Master, may have been milled to fit a set of heads that have been milled and or a heavily decked block and I'd double check the dist hole, for alignment. Set the SM manifold on the block w/o intake gaskets, but with the end gaskets and put the dist in. Check the fit on both sides and see how even it is, rotating it, back and forth on the dist.