Porsche knobs will fit fine on B&M, Schnell and even the knock offs on ebay.
I put a B&M into my '99 986 and thought it was fantastic! Sometimes a little stiff when cold but otherwise nothing short of a great mod. Another alternative, to keep the buttery smooth shifting but not quite as short, is to go w/ a stock shifter from either a 987 or 997.
Good luck and stop rowing your Porsche
