For a preban AR you want to sell to one of the occupied territories, I would put it on gunbroker with a properly worded ad. And good pictures. That will maximize the value, those few states can?t get a new one so they are in demand.
There are a few of them up for auction at any given time. I recommend taking a hard look at a few of those ads.
I?d be curious to hear how it goes. I have a preban Eagle Arms I?ve been considering doing the same with.