Comprehensive details here;
Futura gained ABS, Cruise, Full Instrumentation and upgraded Sound, Colour coded mirrors and different wheel trim.
The 'Classic' was a run-out special type pack to use up all the EA-ED accessories before the EF came out and was available on both Gli and Futura. It included alloys wheels (of varying descriptions - including the yet unseen EF style when they ran out out everything else), free air (it was still an option) decals (woopee) and maybe a few other bits & pieces. As an example mine (Gli Classic) also has the XR red trim strip but plenty don't, I suspect it was late in the series as it originally had the EF style alloys.
Fairmont had plusher trim, different wheels, electric glass and so on.
These days I'd be basing a purchasing decision on condition rather than what they started life with - they all ran down the same assembly line so are all basically the same.
Mine will be sale sale shortly (pm if interested) detail in sig.