I assume you've checked out the wood floor deck and the frame for rot and rust. If it's all good, I'd just remove the carpet and replace with lite weight floor of choice.
Replacing floor covering on an old trailer would be WAY down on my list. I'd start with top replacement/repairs. Most old trailers I've seen so far have deferred maintenance by way of leaking ceiling vents, bad plumbing vent seals, and bad window and door gaskets. Then I'd check all the plumbing tanks, pump, water heater, air conditioner, heater, stove/oven, and refrigerator.
There's the small matter of three electrical systems.
When all the maintenance and repairs have been done and all appliances as well as fixtures have been accepted, repaired, or replaced . . . then maybe I'd start to think about floor covering. Just my .02