Brian, if the cylinder block (same year/model) will accept your crankshaft, camshaft, roller cam followers, etc, all should be OK.
As for the casting core plugs (aka welch plugs), brass would be best, although if this will soon be fitted with a closed cooling system, the brass welch plugs may not be necessary. I would go with brass..... the cost difference is minimal.
Likewise with the head gaskets...... Marine if raw water cooled, high grade automotive if soon to be fitted with a closed cooling system.
I agree, have the cylinder heads and intake manifold magnafluxed.
When you reach the point of adjusting cam followers, use the tried and proven 8 stop static procedure..... not the 2 or 3 stop!
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