GM's massive in-house stamping operations long have been considered among its biggest trouble spots, but executives of its Metal Fabricating Div. say they are getting a handle on efficiency and quality issues. Two years into a five-year, $850 million capital spending program, they say die transfer times were reduced 68% from 1994 to 1995, and average strokes per hour, a key productivity measurement, improved 17% during the same period. Most importantly, Joseph D. Spielman, vice president and general manager of the Metal Fabricating Div. and Manufacturing Centers, says the division now is in the process of whittling down 57 varieties of major stamping lines to six basic configurations capable of producing many different parts. The upshot: GM stamping operations are making productivity leaps, but still have a way to go to compete with the world's best.