There were four different steering levers used on the MGA (eight if you count left and right). The keyway is in the bottom side of the arm. The tapered hole for the tie rod end attachment is larger at the top (ball joint mounts on top). The forward end of the arm angles toward the wheel (away from center of car). Therefore, the last part at bottom of picture (no keyway showing) is a left side part, while the others are right side parts.

The part at bottom of picture is for MGA 1500 cars through car number 54246 (July 1958), part numbers ATB4186 R/H and ATB4187 L/H. Notice the smaller thread. This lever mates with the early knuckle only. Other levers mate with the later knuckle. Second part from the bottom is for late production 1500 cars (July '58 to May '59), part numbers ATB4260 R/H and ATB4261 L/H. Other parts are for the 1600 model and the Twin Cam (and Deluxe) cars as labeled. The Twin Cam/Deluxe has a unique knuckle.

Early 1500 drum brake steering arms. ATB4186 (RH) & ATB4187 (LH)
Thin arms with 1/2 inch thread.


Late 1500 drum brake steering arms. ATB4260 (RH) & ATB4261 (LH)
Thicker arms with 5/8 inch thread.


Twin Cam/Deluxe steering arms. ATB4258 (RH) & ATB4259 (LH)
Used with Dunlop disc brakes (and a unique knuckle).

This is interesting that the Twin Cam and late 1500 arms are consecutive part numbers. This implies that the bearing knuckle was redesigned to accept the stronger arm for the Twin Cam application, and the 1500 arm was changed at the same time to use the common knuckle, or at least a similar stronger type arm desgn. The new 1500 arm came into use two months after the first Twin Cam was produced, so maybe they were using up inventory of the earlier 1500 parts.

1600 model steering arms . BTB102 (RH) & BTB103 (LH)
Used with Lockhead disc brakes (and same knuckle as the late 1500)