Here is an EBay truck listing for a 1966 GMC that is stated as original but there appear to have been changes made. Has some nice options.
Dash has the tachometer front-mounted and also has a vacuum gauge. The engine compartment shows where the transmitter is installed on this particular truck; driver-side fenderwell.
Not sure what the Big canister is near the battery.
http://www.ebay.com/itm/181652845097...%3AMEBIDX%3AIT