Tell them to fit the damn tires. There are hundreds of monteros running around with 31's on stock wheels, and they work just fine, no rub, no interference, and the stock wheel width works very well, and in fact, helps keep the tires on the rims when you air down for the gnarlies.

Also tell them that they can't measure. The wheels are 6 on 5.5 lug centers, and there are millions of GM, Ford, and Mopar trucks running around with those wheels.

They know not of what they speak.

Welcome aboard. You got the truck cheap, and you made a good deal to get it, and you learned something in the renovation work, too, right? Nothing worth having comes free. Remeber that one and it will help you in later life.