We own a 68 buick riviera, it has a non original 430 engine in it now and needs overhauling. We also have a 455 72 buick motor that runs better. We are trying to decide which engine to fix and put in the 68. This is a really nice car inside and out. What is your opinion on which motor too overhaul.We are worried about the oiling on the 430 and the 455 seems to be a more powerful engine.