Look for additional indicators - single 3/8" fuel line, 4 leaf springs, proper Muncie speedometer cable exit, routing and clips, reinforcing patch for dual exhaust cars on the outside of the rear half frame behind the driver's side rear wheel, and double check the top of the cowl and behind the heater box cover (more difficult) to make sure of the VIN you have. If the engine is supposed to match, post the stamping and the VIN codes if you want to generate some competent opinions. Most everything can be faked nowadays, always a good idea to scope everything out if you have no documentation.
Welcome to the CRG -
Regards,
Seve