Looks like i also added to the confusion hehe,,,I just edited my previous post.The mid close and ultra close 56 4 speeds were F4W56L not F4W56A.
56a 4 speeds were revised to be "abit stronger".
Which kind of explains the reputation of the 56L 4speed close ratio gearboxes...
So there was no 56A 4 speed close ratio gearboxes from datsun competition??

quote from tech wiki

F4W56A is the 1973-1/2-revised version of the F4W56L that was mounted on the B110 series. Modifications have been made on the following points to strengthen the gears and bearings, and to improve lubrication performance as well as noise and vibration proof at high-speed driving.

Strengthened gears and bearings: Although there is no change in the gear ratio, each gear has an increased width by 0.039 to 0.079 (1 to 2 mm) and the countershaft, front bearing and main shaft bearing are strengthened.
Improved lubrication performance: To ensure proper lubrication in the rear extension bushing, an oil dam is installed in the center of the extension.
Reference: Service Bulletin Vol. 188 "Introduction of New Model Datsun B210 Series" page 69, July 1973, Nissan Motor Co., Ltd. Tokyo Japan Telex: NISMO.