The Ford Motor Co. manufactured and sold subcompact Pinto automobiles for six years after more than 40 of its own crash tests showed the fuel tank could easily rupture and burn in rear-end collisions, a California-based magazine charged today.

Mother Jones, the magazine published by the Foundation for National Progress, of San Francisco, claimed that Ford could have prevented at least 500 burn deaths by installing a $1 plastic baffel.

Instead, Ford lobbied vigorously against tightening of federal highway safety standards until it was forced to put the device on its newest models, according to Mark Dowie, general manager of the magazine and author of the article.

Dowie said he obtained a Ford Co. internal memorandum that shows the company conducted a cost-benefit study of proposed modifications to its fuel system, and concluded that the benefit in terms of lives and property saved would be under $50 million and the cost of changing the design would be $137 million.

Ford Vice President Herbert D. Misch said the company was studying the article, which he said "contains distortions, and half truths," and will comment further later.

A National Highway Traffic Safety Administration official said the agency did investigate some cases brought to its attention by Ralph Nader's Center for Auto Safety in 1974 but found all involved crashes at high speeds.

Nader, speaking at a Mother Jones news conference here yesterday, demanded that Ford recall all 3 million Pintos with vulnerable fuel tanks and install $11 rubber bladder fuel cells to reduce the risk of fire.