I've had both ductile iron and aluminum main caps installed on multuple blocks at several different machine shops, all where two bolt main caps. The new caps, steel, aluminum or cast ductile iron, need to be machined on the mating surfaces to the block and sometimes the sides that should be a interference fit into the main cap register need fitting also. Once you have them in the ballpark on the I.D. on all five new caps they will need to be either aligned honed or aligned bored and honed to get the proper tolerances for the main bearings fitment and thrust clearances set properly
I wouldn't reuse the stock main bolts on any of them, buy a good set of new main studs to start with and use them
IHTHs
