AMC's motors were all their own. They used a GM 2.8L and Buick 350 V8 plus 225 V6 in early Jeeps (before AMC took over) and Iron Duke 4 cyl in some '77-'83 AMCs and a few postal Jeeps prior to '84.
External parts like alternator, ignition system, carburetor and power steering do not change the manufacturer of the internals of the motor. Ford and Dodge also used Saginaw power steering components for many years. Did that make them Chevy? (I used that on a Mustang guy who tried to tell me the 360 and 304 were made by Ford because of the Motorcraft ignition and carb. He got REALLY tweaked by that!)