My Rv is a 35ft class A with the 8.1L V8. I have driven it from the east coast to west coast twice and all over the Rocky mountains towing a Jeep Liberty. My gross weight with both vehicles is 26,000 lb and we have not had any problems pulling the mountains but don't expect to go up real fast. I'm not familiar with the 6.0L but with your lower weight I think you will be ok
MoCoTom - Noted in forums that you have a Workhorse engine. I'm a new owner of a 2008 Four Winds 5000 31-foot with the Chevy Workhorse 6.0L V8 OHV engine and currently 16,500 miles. We aren't traveling with the pandemic but next year hope to travel from Indiana across the Rockies to LA and then up to Banff in Canada and back home with 2017 Chevy Equinox in tow. Does the Workhorse have the power we'll need?