The cab and front sheet metal are all identical on the 10 20 and 30 series trucks from 60-66. The only real difference is how the frame was made since the 1-ton is much beefier than the 1/2-ton. A really good source for the dimensions of your truck is the restoration package that you can order from Chevorlet. That's where I looked this up at.

Drew
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'66 C-10 stepside