Quality Chevy?
I've never had to do a credit report for a vehicle I've ordered. Every dealership I've dealt with throughout the country has only required a deposit, whether it's for a custom order or a dealer trade. One possibility is that the dealership is located between 2 large Marine Corps bases, and they've probably dealt with more than their fair share of stupid jarheads. I say that as a Marine Corps veteran, so I have some firsthand knowledge due to being one of those stupid jarheads myself many years ago -- young, dumb, and had eyes bigger than my wallet could afford. If you want, tell them to pound sand with the credit report, but you don't mind putting down a considerable, but refundable, deposit. Cash talks. Bullshit walks. A credit report doesn't change the fact that you could always change your mind later and not buy the truck.
Edit: Another thought is they're trying to commit you to purchasing through their in house financing partners so they could also make some money on the back end of the deal. There is a financial incentive for them to do this. My last purchase was financed by my credit union. Dealership never got to run my credit. I took them a voucher they needed to send to my credit union in order to get paid. When I told the dealership the interest rate I got they said they couldn't even come close to it.