The 1981 Toyota 4x4 4 cylinder 6 lug rear end will use the G/22-2041-529 ring and pinion. A 1981 2WD 4 cylinder Toyota will have a 7.5 inch 5 lug rear end and would use a G/22-2042-529 ring and pinion. There was also a 1981 Toyota 1Ton 2wd 5 lug rear that was an 8 inch diff and it would use the G/22-2041-529 the same as the 8 inch diff in the 4x4.