I had a spare set of EB48.2 rear shocks (which are the same as EB48.3 front shocks) and I get 120.5 for length off of the vehicle and fully extended, from center of eyelet to center of eyelet. I screw things in extremely tight (shock cap, eyelet, and cartridge...and I mean take a full size crescent wrench to it and crank on it kind of tight), so if anything mine might be slightly shorter than some others.

One thing I will note though, is that with your mention of 15-20 short I think you may have the EB48.2 shocks (without looking, of course), which are also the same as the SCT410.3 or EB48SL shocks. My front measures to 105 on my EB48.2, but 120 on my EB48.3, as they're sitting on my shelf right now with my setups on them (which both have mostly full droop on the front).

Please measure the shock body length and the shaft length, as those should make it obvious where the issue is.