If you are wire wheeling it clean and are not looking for a show truck, you can just paint with semi gloss Rustoleum. Easy to touch up later. Check POR web sites for brushes or on the can. I used it on a motor, but bought the whole system. Pricey but came out nice. I have to say I don't see a need on a frame, BUT....I live in AZ. FL? probably so. Buy the time you buy the metal prep and enough POR you will be into $125-$150. Rustoleum is $6 per can. I am cheap as you can tell. I do like the terms "cost effective" and "value added".
This may get moved to exterior paint, etc.