When bottom end bearings are repoured, the machining of the babbitt journals is keyed off the camshaft center line so it's generally not an issue to need an oversize cam gear. If the cam journals in the block wear excessively, they can be align bored for bushings. This is not an uncommon repair for well worn A&B blocks. It requires that the boring process be carefully set up to original bore center line to keep gear contact within specs. If it's off center, the need for gear change could be the only recourse unless the discrepancy is corrected with a more accurate machining process.