Just wanted to chime in since I finally did this mod on my 98 legacy l after procrastinating for like 2 years. Definitely worth the effort. IMO, best upgrade I've done since i upsized my wheels to the GT size a few years ago.
I used the subaru shoulder bolt and a pretty low profile prevailing-torque type of locknut from oreilly - a doorman part I think.
I ordered the 2 bushings for the shifter itself, but unfortunately they are a different size on my legacy, so I have the original neoprene type of bushing in there still. I think that's where the only remaining play is coming from, and it's literally probably only about 1/8" in any direction.
One thing I didn't see here elsewhere - I was able to do this without removing any crossmember or exhaust heat shield. It's definitely tight in there, but I'd gotten very familiar with this area from all the times I'd tried other lesser fixes with nylon washers, etc. I had the harbor freight punches, did the center pin, then the larger one and it was a snap. This is a salty MN car, so that's saying something. To get it back in, I just put something a little smaller than the pin into the hole from the opposite side to maintain the alignment, and then drove it out with the pin ducktaped to a slightly larger punch.
My only regret is waiting so long - no more chatter, no more 6" of play. I was stoked every time I drove my car for days after doing this. Do it now!
@classicaddict - the 3/8 bushings end up resulting in something like a pressed fit in this joint, and the result it perfect. It's just dumb luck.