Robins Rails kits

I'm afraid the answer is maybe.

IIRC, Robin's Rails got their base kits from a couple different sources, which may or may not be roughly compatible with Athearn.

We'd probably need to see pictures or measurements, unless someone knows based on the model designation

Measurements are necessary if we're going to help you.

Also do you have any nearby train shows? Bring the body with you and you can probably find an appropriately sized frame on a car for a buck or two in some dealers discount bin.