In the early 1980s the French (and other AMX-30 users) were limited to the HEAT OCC-105, aka Obus G, with the OFL-105 APFSDS being available in the mid 1980s. It is known France bought a test batch of M735 but as far as I know only for tests. The bore design of the DEFA F-1 was optimized to use the OCC and could not fire APDS. No such problems with APFSDS rounds.
The DM23, aka M111 became available in the late 1970s so I doubt the Leopard 1 fleet was limited to APDS until the A5 upgrade. As mentioned, vehicles fitted with manual FCS only neded the reticles being modified. This was done to the M60A1 fleet, for example.