1959 (and many other years) GMC 1/2 ton trucks came from the factory with caster shims installed. I assume that Chevy trucks did too. Stock shims are described in the GMC Master Parts Book as "shim, front spring, 2 inches wide by 3.88 inches long, 0.093 inches thick at one end (the front) and 0.195 inches thick at the other end". There was also another shim listed with the same dimensions, except 0.281" thick at the rear which would increase the amount of caster.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
