Fabio the Tamiya Quad kit is about 1/32 scale and apart from the windscreen frame is a pretty accurate reproduction in the front sheet metal. So I suggest you use this kit and scale down from the measurements of it's parts as I know of no correct scale drawings available. I cannot find the 11/12 cab measurements I took from a few wrecks to build my 11 cab Ford G/S unfortunately. Cab measurements are the same between all models both in the 13 cab and 11/12 cab series although I think the front mudguards are narrower on the 8cwt models. The Ford models have a different in cab engine cover to the Chevrolet and the grill mesh differers as well as a few other minor details like mirror positions.
My 11 cab F60L model
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Cheers
Cliff Hutchings
aka MrRoo S.I.R.
"and on the 8th day he made trucks so that man, made on the 7th day, had shelter when woman threw him out for the night"
MrRoo says "TRUCKS ROOLE"