Nothing like a good Epoxy primer. I've used the Omni line of PPG with good results for what it costs. I also seen some pics of a fellow member evill which he sprayed Southern Polyurethane's black epoxy primer on his 911 Porsche project. Here is the link if it works.
My 911 Project
Using the black I think would be a good idea because it looks like it would show imperfections better. I don't think the SPI is real expensive either.