I bought an 03 GMC Sierra last fall. Got the GMSD ($3500), a rebate ($1000 at the time, I think it's $2000 now) AND a conversion customer discount ($500). The conversion discount, or whatever it's called, is for customers who own another make and buy a GM vehicle. I provided them a copy of the title of my 1942 Ford and they took it no problem.
I got local financing for 4.25% in lieu of the 0% financing.
FWIW, when I was shopping, I called the local Ford and Dodge dealerships and they were all willing to meet those same deals. I just got a better trade in on my 99 Silverado from the GMS dealership and I really like the truck.
EDIT: I forgot to mention that this particular truck had to be located. It actually came from Wisconsin (I live in central IL).