Sounds like your friends Vette has water in the oil. When the oil looks "milky" it usually means there is water present. This can come from either condensation or coolant leaking into the oil. If his oil pump was blocked, he may have damaged the motor due to lack of oil. This can result in overheating and a cracked or warped head, cracked block, or blow head gasket. I think I'd be running some tests on that motor. I think a cylinder leakdown test is probably in order, and maybe a check of the coolant for exhaust gasses. There are dyes available that you can put into your cooling system that will show up as flourescent under a blacklight if there is carbon monoxide in the coolant.