Here are a few options. Use the AMT 454SS pick up and the AMT C-3500 Street machine(for the grill). If you want the 1989 quad lights, you could graft them from the original AMT C-1500 kit or 1988 promo. Another option is Motormax diecast 454SS or Sierra GT pick ups. The GMC grill has the 1990 style lights. The GMC I have has the step side bed. The Chevy is a fleetside. All mentioned trucks are 1/25 scale. The diecast detail is pretty good, just the way the doors hinge makes it toy like. All are currently available on ebay.
Plaskit has what your looking for, part #T110. It comes with a set of 6 black resin tires and 6 wheels. They look similar to GM Topkick wheels, 19.5" 4 spoke wheels. Quality is good on his products. Here's the last email address I have for them. They are based out of Canada. I ordered mine in 2007. They were $18 back then. Craig email@example.com
Sorry for the delayed response, I haven't been on the site in a while. The cab and bed are from AMT's C-3500 phantom dually kit. I had lowered the original kit and made bigger rear tubs to fit the tires.
I ordered quite a few parts this Spring prior to seeing the 2015 health issue posts. I received all of my parts I believe within 4-5 weeks. Maybe they received so many orders they are trying to catch up similar to the Modelhaus?
I had one of those MPC 4x4 Dodge kits. The tires were 1/20th scale street tires. The Dessert Dog Offroad tires on the Fall Guy pick up will fit on these rims. My only worry about sleeving them would be the centers would be too large. Craig