tufcj
If it's an I-6, I think you can use a GM I-6 HEI and just change the drive gear to AMC.
For the V-8 HEI, the ones I've seen anyway, they machine the bottom off the housing of both distributors, then weld the AMC lower to the GM upper. Then the shaft has to be machined shorter and to fit the AMC oil pump, and the AMC drive gear installed. With the work involved, it's probably worth the $250 or so they get for one on ebay.
Bob
tufcj
pyagid
what TufCJ said. FOr my 6cyl i took a GM HEI, and a AMC v8 drivegear dropped it in, and fired it up.
To bad it is not that easy for the V8