I opted to go with a Urethane based, high build primer from Paintforcars.com. They sell quite heavily on ebay and the price was good. I consulted with Finishmasters in Grand Rapids on what primer to use, as I was initially going to use an acid etch first, then go with a build. When I told the guys I really wasn't looking for a concours paint job and the end result was going to be a flat finish anyway, they said that a Urethane high build would work fine over metal. The primer from paintforcars was 88.00, plus a quart of reducer took me to around 100.00.
The first batch I mixed up a little too thick and it shot on like undercoating. Luckily it laid down a bit, so no biggie. Overall, a very easy primer to use, and built-up very nice. Finally, the rear doesn't look like a hodge-podge of multi-colored primer and metal! From here I'll start working on the front of the car (which will be much easier and less time), prime that, block the whole car, and be moving on to paint. I will need to remove the front fenders at some point, as when we do the body swap, they'll need to be off.
Here's the finished result after two coats.
