X2 on the babbit bearing issue. They don't take well to high rpm or increased load. The babbit material is very thin and is splash-oiled in the 216. It would be an expensive proposition to get the rods machined for inserts, change the pistons out from cast-iron to alluminum, and modify the oiling system for full pressure. All of these upgrades are included in the '54 and later 235's, a much better candidate (IMHO) for what you want to do.
