The VIN won't help you, but the buck tag mounted to the firewall, directly behind the carburetor, will. If it's a true Indy truck, the word INDY will be along the bottom edge of that tag.
This same interior was installed on all '77-79 F-series trucks with the Freewheeling package as well, so the parts aren't as tricky to find as you would think.
The GT Bar (called that due to liability restrictions, Ford didn't want to be responsible if someone *rolled* their truck and died) was standard on all Indy trucks, but the front push bar was optional.
