The difference between the two weapons (M101/M102 and M56) is slight, as far as muzzle velocity goes:
M56 - Muzzle velocity 416.0 m/s (1,360 ft/s)
M101 - Muzzle velocity 1,550 ft/s (472 m/s)
M102 - Muzzle velocity 494 metres per second (1,620 ft/s).
Essentially, where the M56 wins over the M101/M102 is in it's lightweight construction and ease of disassembly and reassembly for pack duties. Where it loses in in it's durability, which is why the Australian Army replaced it's M56s in RVN after about two years use with M101s. While not a worry for airborne use, it's lack of wheel bearings on the ground mount prevent it being towed anywhere far or fast.
The M56 would require modification for extended use. It's mount and it's tube would require "beefing up" and so would it's breech assembly.
Interesting discussion here, BTW, about the 105mm's recoil on the AC-130.