Are you talking about a vintage Hi-Lo travel trailer that raises and lowers with a cable-and-pulleys system? If so, you might contact a vintage trailer restoration shop. One of the best-known (and most highly regarded) ones is Flyte Camp in Bend, Oregon. You might call them at (541) 639-6141 for an estimate. Even if you don’t plan to bring the trailer to them for restoration, they might be able to give you an idea of the job complexity and estimated cost. It probably won’t be cheap whoever does it.
TJ