With a few exceptions. The 4.3 was only offered in a half system. The 350 Mag may be a half system or a full system. Most of the 350 mags were bravo drives and the block mounted raw water pump pushes more pressure and volume than the leg mounted raw water pump. Putting too large a heat exchanger on the 4.3 is not a good idea. Mercruiser has about 75 active heat exchanger part numbers for a reason.
