For brake parts, radiator hoses, etc. are what I'd classify as chassis specific parts. They certainly are used on other vehicles but you probably will have no info on the specific part uses. A FORD F-350 is the closest that may use similar parts. The chassis will be about 1 year older than the RV. I've followed two routes to find special parts; call Freightliner or take the part off and take it to many part stores until you find a match. By parts stores I mean car & heavy duty truck parts stores. Freightliner has been very helpful in the past, but my last call to them for this chassis was 5+ years ago. Even at that time all they had available to them was paper books to look up the info. Our local heavy duty truck shop has provided good support too. Most major parts will have parts numbers or casting numbers on them that can be used to track down a replacement.
The chassis was also used for StepVans, UPS & FedEx trucks, etc. Another source for parts is Mill Supply
. Their phone support is good too.
I did have to replace one of the power steering pumps due to a housing seam leak. It was a special order from Freightliner, but have a FORD number on it. The other power steering pump powers the brake's hydro-boost system.