I've looked and all I can find is people wanting to paint their silver engine black, but I just want to paint the whole engine silver again. The stock powder/paint looked pretty beat up after 25 years. So what paint would hold up best for this?

 

Just go to your local autoparts store and by some High Heat/Engine paint in any color you want.

 

Your engine is bare aluminum.What Harley calls"natural" The only way to make it look as original is to bead blast it. As enodrano says,auto store high heat spray bombs.