Niles,
What don't you like about the stock shifter? How do you plan to drive the car? Aftermarket shifters will accelerate the wear on the syncros due to the quicker shifting action that they all offer. But most offer externally adjustable hard stops, which keep you from over-extending the shift forks. Personally, I added a Pro 5.0 shifter to my tremec (3550) but I haven't driven it yet
. I have a stock T5 shifter handle mounted to it and it fits my car perfectly. I like the idea of the hard stops and am also used to a short throw shifter. But if I hadn't come across such a good deal on the shifter, I would have been quite happy with the stock TKO shifter on my 3550 (the TKO is the same as the regular 3550 shifter but with about a 30% shorter throw). I have driven a mustang with this setup and it was very nice. Plus, I don't plan on powershifting my car, but rather shifting with my wrist, hence the stock shifter would have been a-ok
.
To answer your other question, there are several aftermarket shifters on the market. Do a search over on the corral.net and you'll find the most popular shifters are the Pro 5.0 and I believe the Steeda Tri-Ax.
Mike