Given cubic amounts of money anything is possible - but in this case it might require some rather massive re-engineering of the transmission tunnel and mounting points, plus probably driveline and shift linkage.
Possibe - anything is --- practical - hardly.
Best way to achieve this is to sell the '93 car and buy an E46 M3 with the 6-speed installed. Probably less expensive in the long run than what you're trying to do (only about $29k difference in value between a '93 any BMW and an '03 M3..)
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