AMC auto workers may 'invest'

American Motors and the United Auto Workers intensified talks over the weekend for a third major auto contract with substantial concessions by workers following the precedents set in union negotiations with Ford and General Motors.

Monitor correspondent Ed Townsend reports that although one negotiator said ''many issues'' remained to be settled, an agreement appeared in the making. Under it, workers would ''invest'' in AMC's product development program by giving up for 22 months part of the wages and benefits they would normally receive. They would regain the money with interest perhaps early as 1984.

Meanwhile GM's 340,000 workers will begin voting this week on a new contract which could save the company $2.5 billion or more. The union's General Motors Council approved the agreement 299-to-25 on March 25, virtually assuring its ratification.