Chances are that they used the 'lighter' GVWR on that chassis.
With Fords the motorhome GVWR from 1990 - 1997 was the 17,000 pounds that I have. With GMC, if I had bought my30' Bounder 14,250 pound motorhome on a GMC chassis, it would have come with a lighter weight GVWR chassis, 15,000 I think. The GM motorhomes are about 500 pounds lighter than the Fords.
You are right, there is a 3,500 pound tow limit on all the Fleetwood motorhomes before around 1999, when Ford stepped up to the 18,000 GVWR chassis, and GM also increased their GVWR around the same time. Fleetwood was losing customers who wanted to tow 5,000 pounds, and they finally increased their tow limits.
Mainly it has to do with frame extensions. Mine is only about 18" long, and I have a 190" wheelbase. However the 38' Bounder has the same factory 190" wheelbase and a 'tag' axle, with electric brakes, 3,500 pound weight rating, and about 10 feet of frame extension. It would be scary to tow something 7,500 pounds with all that frame extension with a 38' motorhome, but with your shorter frame, it would be no problem. So Fleetwood did not want to have say a 5,000 pound hitch rating on the RV's with a short frame extension (or non like a 25' class A would have) and then rate the ones with a long extension for 3,500 pounds, so all the brochures say 3,500 pounds, simple for them, bad for those who want to tow something heavier.
I would not worry much about towing 4,000 pounds with the factory hitch. It is way out of warranty anyway. The factory hitch is strong, and probably mounted directly to the GM chassis, not a welded on frame extension.
I toured the Riverside CA Fleetwood factory twice in 1996, before ordering my 1997 Bounder. It was interesting to see the frame extension process, how they build the floors, walls, roof system, laminate it all together, and install all the cabinets, rooftop A/C, and such. They push all the new RV's around the production floor with tow dolly and a golf cart motor attached to it, plugged into the trailer hitch. This is why all Fleetwoods of the time had a trailer hitch, it was what was used to move them from the frame department to the paint booth. Then it was driven out of the paint booth to the water test area.
What I would be looking carefully at is the roof. If it is original, pass on this RV unless it was garaged, and the roof still looks 'good'. Chances are that the roofing material was replaced, or at least coated. I had to coat my EPDM roof and used a paint on style coating.
IF the insides look leak free (no stains on the ceilings) then it is a keeper. You will want to coat the roof sooner than later, so that you do not need to replace the roof. It took about 8 gallons of this product to give a good thick coating on my roof.
http://www.epdmcoatings.com/videos_play.php?vid=25 If you can paint your room, you can paint this stuff on the roof. It is that simple.
Fred.
