From my research it looks like 1977 was a transitional year for GM in engine color, going from Chevy Orange to Corporate Blue. Since the I-6 in the truck now was blue, I decided to keep that theme. I ended up using Duplicolor DE1608, known as "GM Blue", on top of a few coats of rust-oleum engine primer. It was a little bit tough scuffing down brand new polished aluminum parts, but the end effect was worth it