Bradbilt makes a good point about the diff.... 7300 may be spec'd for the tallest rear end. Some guys went with the 460 - if they just needed a local service truck that didn't run a ton of hours, they saved a some dollars on the dealer invoice by going gas.
I know someone with pretty much that exact truck, except stick. 460 pulls fine, it's a strong truck.
If you plan on having it around for a while, consider upgrading the trans cooler. It's a worthwhile thing to do in general, but unless the ATF was regularily maintained, an original trans cooler can be somewhat (or very) restricted by sludge build-up by now. You could just take the original cooler off and properly clean it out, but with how low cost a decent aftermarket higher capacity cooler is, that's the way I'd go. :2cents:
Pls. let us know if you get an final answer from Ford, and what the rear-end is.
Rgds, D.