Les, the C10/C15 is the same differentiation as the earlier 3100/3200, just not badged that way in the 67-72 era - the actual designations were CE10704 for the short and CE10904 for the long - I've had a number of 67/8's myself .... the Longhorn started in '68 .... and there were no 7' beds, as indicated in the GM info, they were 78.25" or 6.5' and usually referred to as 6'
Bill
