Question to the group - what Asbestos content can one expect from an early 1970's MoPAC Caboose?

The heat shield behind the stove should be the only place, if at all.

Most of those heat shields should be sheet metal with or without standoffs. If there's insulation in the walls, it's most likely fiberglass as that's been in general use since the 40's. I can't think of any reason there'd be asbestos pipe wrap anywhere on a caboose. I'm thinking you're good to go but if in doubt, get a test/sample kit and send some off for testing. Costs around $50 or so.

It could be in the flooring material.

Good point. I forgot to look down while thinking about this. Wood, no problem. If it's the typical black sheet flooring, there is generally a chance that asbestos is in there though not likely. If it's stuck down with the usual old black mastic, then there's a much higher probability there's asbestos in that. If someone put the older asphaltic, vinyl or linoleum tiles in there, then there's a good chance there's asbestos. Best advice, test it to be sure.