also....if i don't know the manufacturer or a part #, how do i find the correct sending unit. currently, my guage reads 3/4 at full and i can go 200 miles after empty. the dimensions of the tank are....31" X 28 1/4" X 12 3/4". this is on an 85 suburban k10, this is not a standard 31 or 45 gal tank.