One source that has DELCO Alternators available that fit stock AMC Brackets
is Kennedy American in Ohio - 614-879-7283
http://www.kennedyamerican.com/index.asp
They have 100 amp and 140 amp in both plain and chrome.
140 amp Chrome = $299
140 amp Plain .... = $229
100 amp Chrome = $269
100 amp Plain .... = $209
They don't give the specific part numbers, don't know if they'll tell ya if ya call.