The A320 of today has come a long way from the initial -100 delivered in the late 1980s with the list of what they did not have in comparison with one coming out of the factory today being extensive.There is also a huge list of customer options available to a buyer. I first encountered GPS in a factory delivered A332 in 1999 but this was when the accuracy of gps was deliberately degraded to 100m by the US military.
For the A320 family it was probably the introduction of the Honeywell pegasus fmgc that brought gps into use. Who remembers the original fmgc fit that had the tuned VOR at the bottom of the Prog page?
There is a history of Honeywell fmgc aboard Airbus in this document
https://aerospace.honeywell.com/cont..._A330_A320.pdf