G refers to what is usually found in the lower contact points of the rear of the front fenders behind the dog leg type trim, right in the wheel well. Lots of muck gets trapped down there and it rots that spot.
Other than that, check for frame integrity of the floor pan, rear subframe assembly, and general cleanliness of all bolt hardware on the suspension. This will help determine how hard it is to tear things apart should they ever need to be.
Door bottom seams, trunk seams, hood seems and windshield edging are the next spots of interest, including around the sunroof location should it be equipped.
If in good enough condition for your purposes, consider the condition of the engine and the proper shifting of the transmission and lack of noises from the center diff assembly and rear driveshaft/rear pumpkin. All of which is correctable, but would make for wiggle room on the purchase price of the car.
Hopefully it is a worthy example of a GVR4, for your sake, but be aware of sketchy looking mods and a user that may or may not be able to tell you why certain mods are installed and how they were performed.
We try to help anyone that can acquire one of these cars, but we rarely say walk away without very good reason, and stating the reason(s) should there be any. Know what you want out of the car, use that for you pricing and restoration budget. Don't expect a free ride from a car of this age, nor not having to wrench on it to get it to some level of certain repair status to assume proper daily, or other, driving status. There is a thread in the Newbie section I believe, probably a stick on what to look for when buying a car, a GVR4 or any other car from Mitsu of this vintage.
Enjoy the sales process but bring a knowledgeable third party who can advise you on obvious stand outs with regards to condition, driveability problems or lack of maintenance, and be able to work with the seller with these issues. Even blown shocks and bald inner tire treads might not be super visible from certain angle and with certain mods.
Don't buy a car at night and don't buy a car in the rain.
My thoughts.
Take your time and don't get swept away with nuance if the owner/seller gets all nostalgic and starts talking about pedigree, rally history, this car can take 400HP; critique the car properly.