Short answer: NO
There is no such thing as a Holiday Rambler service or mechanic manual - HR never produced such a thing.
Freightliner Custom Chassis (not the truck company) may have had some chassis manuals for their motorhome chassis but most of the chassis components are generic parts (engine, tranny, front & rear axles, air compressor, etc) and documentation on those can often be found online. You can also call FCCC Customer Service at 1-800-FTL-HELP and get help. Have the last 6 digits of the chassis VIN handy and they will look up the specific in their database.
Cummins and Allison also have support for their components. Have the Cummins engine serial number handy if you call them.
Former owner of 2004 American Tradition and several other RVs
Home is West Palm Beach, FL