From anybody that sells them. Just buy them for a pick-up. The cabs are the same from 1/2 ton to 2 ton and up. I've used Chevy Duty, Brothers Trucks, The Truck Shop, Impala Bob's, etc. Get yourself a copy of "Custom Classic Truck" and/or "Classic Truck" magazines and search the vendors in there. Most catalogs are free or have an online store to shop from.
Happy hunting,
Scott

Scott Ward

2 1948 1.5-ton Loadmasters
The red one and The snow pusher
1 1950 3100
1 1955.1 Chevy 6500
1 1954 Chevy 6500 2-Ton
1 1955 1st Series COE 5700
1 1963 K20 (454)
1 1964 C10 (350)
1 1951 1.5-ton Dump Truck
1953 and a 1956 Ford F800

Raising a teenager is like trying to nail Jello to a tree!