My current project is dropping a 455 into my '87 Supreme, and pretty much everything they said is correct. Unfortunetly I don't have the cash to get started yet...exhaust and rear end build. According to my research the consensus is that the increased deck height on the 455 doesn't allow the air cleaner to clear your hood, so that's one thing you need to take into consideration. Apparently headers/manifolds are a tight squeeze, and the steering shaft gets in the way sometimes. Additionally, the whole rear end needs to be upgraded.
Hooker makes a set of headers specifically designed for this swap, but they cost just shy of $600. If you can find a used set, go for it, otherwise just buy what you want and beat on them until they fit...that's what i'm gonna do anyway
Hopefully I can start working on mine by FALL...
