The tank I have on pigpen is out of an 85 s10 blazer and I think it hold around 15-20 gallons, its kinda narrow and deep as opposed to wide and shallow like you are looking for though. As far as I know, all GM sending units are the same. In pigpen, as I said, my tank came out of an 85 S10 blazer, but the sending unit is from an 84 carb'd gasser. I am prety sure the hole in the top of the tank is even the same size on the 90's models, but I've never measured to check.