My brother has a 72 mustang and he pulled out the 289 and is in the process of building a 408 for it. So would I have to bore it .040? I think that's it right? What I am wondering is for my build what measurements should I have inside. Meaning like angle of plugs. Intake runners combustion chamber, exhaust valve, valve springs, max lift. My brother told me what sizes he is putting on his but I don't know what is best for me. I don't necesserally need exact measurements just ranges for different possibilities. He is building to put a supercharger and I am not so his build is going to be a lot different then mine.