I'm looking at a NIB Colt small pin Pre-Ban 7.62x39 Carbine for $1600.  It has A2 sights  with a 16-inch heavy barrel and 4-position stock.  Is it worth it?

Only you can answer that one. Not trying to be a smartass but I wouldn't buy a 7.62x39 in a preban & pay the $$$$. Accuracy will not be anywhere near the 5.56 nor the .308, generally speaking.

I'm hearing that mags are also a sumbitch to find.

You could buy a postban 7.62x39 & pay half that & get everything on it except the 4 position stock, that **could** be added after the AW sunsets.

My .o2