[spankyway]

I would use an epoxy promer and possibly a urethane primer over that. The epoxy primer is a good sealer for the base metal and it not a sandable primer. The urethane primer will be sandable but it tends to pick up stuff like bugs and oil from the road. You should also use a primer from the same manufacterer as the paint you plan on using. Paint manufacters do not warranty the paint job unless you use all their products, plus some paints will not work over other primers.