Ford Motor Co. opted for a $6.65 saving per car rather than improve the rear end and fuel system design of the Pinto, former Ford engineer Harley Copp testified today at the company's reckless homicide trial here.

Despite the vigorous objections of chief Ford attorney James Neal, Copp was allowed to respond to prosecutor Michael Consentino's inquiry, "How did [the] reduction in the fuel system integrity of the 1973 Pinto come about?"

"It was a $6.65 saving," Copp replied. He said the decision was the result of an April 22, 1971, product review.

Ford is charged with three counts of reckless homicide stemming from the August 1978 gasoline explosion deaths of three teen-age girls whose 1973 Pinto was rear-ended by a van near Goshen, Ind.

Neal complained that Copp based his testimony on a document from the product review; the document earlier had been disallowed into evidence by the court. Neal also said the subject of the meeting concerned 1974-76 model cars, not 1973s. "This is the most inadmissible document we've come across yet," the attorney said.

Judge Harold Staffeldt agreed not to permit the admission of the document or testimony regarding any other model year cars except the 1973 Pinto, in accord with earlier rulings limiting evidence. But he added he believed the witness was obliged to testify on the 1973 Pinto and allowed Copp to respond to Cosetino's questions.

Copp testified earlier that the Pinto was originally programmed to meet a 30-mile-per-hour rear end impact standard during an August 1969 strategy meeting with former Ford president Lee Iacocca. Ford did not adhere to the standard, the former official said, for cost and profit reasons.

Cosentino said Copp's cost analysis testimony was "extremely important" to the state's case because the prosecution had not yet been able to introduce into evidence crash test films and documents on 1971-72 Pintos due to court rulings. "We've had to rely more on Copp's oral testimony than we intended to do because we could not get documents in," the prosecutor said. "But our full story is not being told."

Copp said the Pinto was "grossly inadequate and the weakest I've seen in cars for the last 10 to 12 years." He proceeded to list the problems with the 1973 Pinto fuel system, including an inadequate crash space for the fuel tank, a weak floor pan, a short filler tube and too many sharp edges -- puncture sources -- near the fuel tank.