I'm not positive , but , I think that by 07 Workhorse had switched to the W-22 or W-24 designation . Either 22,000 lbs . GVWR or 24,000 lbs.
Before I bought my current coach I looked at a 05, 37' Tiffin , on the W-22 chassis , and didn't purchase it due to it's low CCC. ( Cargo Carrying Capacity )
CCC on that coach was under 1,000 lbs.
B-in-L, had an 05 , 35' Tiffin on a W-22 with a 1,300 lb. CCC and was always having trouble keeping the unit from being overloaded . The front axle in particular , when he got to close to the front axle weight rating , the coach handled poorly.
JMHO: Look for the RV's weight sticker ; where the CCC will be listed , and if the CCC is under 2,000 lbs . Personally I wouldn't buy it.
Sticker will look like the picture below , but there is no standard location , so you have to search for it.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.