[tcrist]

Most powder coaters have blasting there on their premises. You could have it all done at 1 time. If you are going to do any mods to the frame you could have it blasted and then powder coated later. As long as you have it powder coated within a few months of blasting, more rust should not be a problem as any rust would be just surface rust and easy for the powder coater to remove.
Suggestion, find a powder coater that has done auto work before. Go onto a "socal" hot rod forum (CHR) and find out from them who they use.

JMO, Terry