urei actually DID make a kit that just screwed onto the back of the unit, over the screw terminals. it had two XLRs that would connect to the screw terminals with short leads. you might try contacting jbl to see if they still have this "model 301 XLR/QG adapter" for the 1176.
but they probably don't. in which case, you'd open the unit, unsolder the wires from the inside of the screw terminals, noting which goes where. remove the screw terminals. make two XLR sized holes, using a stepped drill bit ("unibit") or metal hole saw and the four screw holes to hold the XLRs on. then pop the XLRs in and reconnect the wires. reworking the case wouldn't be "easy" but it would be doable.
far easier would just be making a set of short XLR to spade pigtails with robust hookup wire and leaving them on until they wear out, which could be a long time.
ed