Safe to use Wheel Adapters 5 on 4" to 4.5"?

So, I'm converting to disc brakes up front (65 Plymouth Valiant Signet convertible) so that takes care of the front. The rear I had planned to use high quality billet 1" adapters. I ordered 15x7 front/15x8 rear US Mag U107 rims with 215/65/15 front/ 235/60/15 rear Cooper Cobra tires from Discount Tire. I told them that I intended to use rear adapters, even showing them to them, when I ordered and paid for the package. Today they tell me they are in but, not only won't they mount them, they would not even sell the rear ones to me knowing my intentions! They said they have a new policy about adapters but could mount to spacers. So, I can cancel and order from someone who will mount to adapters or I can explore other ways to get a 5x4.5 pattern in the rear. Any experience, ideas or advice out there? Thanks in advance...

I would guess the tech didn't explain it correctly. When I had an America's tire mount my new tires a few years back they wouldn't re-install the 3mm spacers I had on the front at the time. No problems mounting a 275/35/18 on an 18x9" rim on a '74 Duster, but the 3mm spacer was a no go.

:rofl:

Either way, it's not about the spacer or the adaptor, it's just a policy to limit their liability. Like the alignment shops that won't adjust tubular UCA's unless they install them, it's not about the UCA's it's about 1. Them not getting the money for the install and 2. Liability