Differences A903 and A745?

Yeah the 745 was a teensy bit more robust. Neither had a synchro on first, and the 2/3 synchronizers were very low performance. I rebuilt hundreds of those back in the late 70s. I would not run either one today, on anything but a lo-po slanty. Remember, you cant really downshift into first, without an awful lot of practice which usually destroys the low gear until you learn to double clutch.
Slantys had a lower gearset,IIRC