MONTREAL — UAP Inc., Canada’s largest distributor of auto and heavy-duty truck parts, is considering a take-over bid from Genuine Parts Co., the Atlanta, Ga.-based operator of the NAPA auto parts retail chain.

Genuine, which currently holds about 20% of UAP’s outstanding shares, is offering $356 million in cash, or $28.50 a share, for the remaining 80%.

UAP said members of the Prefontaine family, controlling stockholders of the Montreal-based company, have agreed to sell the 19% of UAP stock they own.

Genuine and UAP have had a long-standing business relationship in Canada, especially through distribution outlets in the West.

UAP distributes, markets, and rebuilds replacement parts and accessories for automobiles, trucks, and industrial machinery.

With almost 5500 points of sale across Canada, its parts network is the largest in Canada. UAP has annual sales of nearly $800 million and employs 5300 people.