Less, what wheels do you have on old chassis? 10 lug I assume. Tires 8.25? Any good tires on them? If so, wish to sell? I see you are from MI, how far north? I'm in NE Indiana.
Keep in mind the fenders arch high at opening, and may look odd on smaller wheeled truck. You may also have axle width problems, new frame wanting to stick tires out past fender edges.
Far as sleepers, there are always ads in those trader brand mags and others, out of MI area and Northern ILL. Pick up the Big Truck trader, some gas stations have selections. OR, truck stops. There are lots of truck suppliers in S. MI.