Winnebago lists these GVWR (chassis carrying capacity)for the 25B:
Chev 3500: 12,300
Ford E350: 11,500
Ford E450: N/A; only available on 27Q and larger models.
25B: 26'6" wheelbase 183" Towing 15,800-12,300= 3500 lbs.
27Q?QP: 27'11" wheelbase 220" Towing 22,000-14,500= >=5000 lbs.
My (E-450) 26.5' RV is ~11,000 empty. Add 350# water and 350# for two passengers, leaves you with ~600 lbs max for cargo. If you can live with that, the softer ride of the 3500 might be fine. Check the real OCCC or CCC sticker inside the cabinet door though, 25B might be lighter (3500 chassis) or heavier (fiberglass exterior) than my example. Chevy likely rides better and has more passenger legroom than Ford. Tow limit is 3,500.
The 27Q's built on the E-450 will give you more cargo capacity, more towing capacity, and a longer (more stable) wheelbase.
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