Since factory wheels to fit this GM bolt pattern are getting very difficult to find, I started looking for options. It turns out mid sixties to mid eighties C-50, C-60, LCF and probably others have the 5/10 on 8.750” bolt pattern. The hub diameter is 6.250” vs. 5.250” of the earlier wheels. Upon inspection, there is enough material to support the smaller bolt pattern.
I found several wheels, they come in at least 6”and 6.5” widths. I drilled the smaller bolt pattern using a rotary table, made a spacer to accommodate the hub differences. There clearly is enough material, strength wise.
If one does not have access to a rotary table, one can use a drill press if the throat is deep enough. Make the hub adapter using a face plate and washers so the diameters will be concentric, make or get some drill bushings to fit the diameter of your 20” wheel lug bolt holes, get or make a few pins to lock the wheels together and go for it.
The silver paint in the picture indicate the smaller bolt pattern, only one nut is attached.
Ed
Last edited by EdPruss; 09/15/202110:06 PM.
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires. '47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle. '54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed. '55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
