OK ,tires are 31x10.5 on 15 inch rims.Now where are we ? Thanks for all the brain cells thinking about this !
Looks like there were only (2) rear ratio's for a stock 1960 C10: 3.90 or 3.38
http://public.bay.livefilestore.com...iCNr-eTGE8mWIkF1PmNQ/Truck%20Axle_ID.jpgAssuming your 327 can handle a cruising rpm of 2600, and a max RPM of 5500:
Trans Ratio = 1
Rear Tire Diameter = 31 inches
Assume a 3.9 Rear Ratio
@ 2600 RPM = 62 MPH
@ 5500 RPM = 130 MPH
Assume a 3.38 Rear Ratto
@ 2600 RPM = 71 MPH
@ 5500 RPM = 150 MPH