It's interesting that the Ikeya sequential shifter in the Zoom article was brought in by Japanese Motorsports for George's 200SX. According to their front page he is their best customer, and if go to; http://www.japanesemotorsport.com.au/partsinstock3 .htm You can by the "slightly used" sequential shifter for a 200SX/Silvia S13/14 for only $1900! A lot of money for "no improvement in shift speed could be detected" type performance!
A shorter shift for the R154 would be desirable, but I've found that trying to shift too quickly (esp 2nd to 3rd) causes me to sometimes miss the gear. Now I could a crappy driver, or the box could be a bit hammered, or maybe some things (like that long, slow shift) you just can't change!