With a 455, most likely the surface rust was caused by condensation from sitting for a long period of time without being run. There are some simple tricks for keeping oil in the bottom end on the 455s too and while tou have the push rods out cleaning them, you can slid pipe cleaners in the holes to restrict some of the oil up to the heads. Psycho Squid has some other tricks he used on his olds to make it hold together on nitrous and later blown. Good luck with the winter project. Boating somehow is a year round job.
Cy