Look for:
Bolts on the engine and fittings that have obviously been removed/replaced.
Heat discolouration on the rotors.
Holes in the body where things have been removed.
Mismatched paint.
Service records if any.
If you get a VIN you can compare it to the numbers listed in the Service Bulletins here -
https://www.ft86club.com/forums/showthread.php?t=21868