Cab to frame measurements

[Oldtruckwelder]

Need your help, years back I grafted a late model camero clip to a 1957 stepside. I have been putting all the sheetmetal back on and trying to get the gaps presentable. Doors gaps around cab looks good, fender to door gaps are close but I'm convinced the cab needs to either raise on front mount or lower on rear mount. Has anyone transposed the measurements from the truck manual, the reason I ask it shows a instrument hole from inside of cab to the frame and that hole is not useable from the firewall side to be of any use.
Thanks JT from SC