I Triked my '99 I/S last spring. I wanted to build it myself, so that left me with two choices, as all the others will only sell through their dealers. I went with a kit from Triwing Industries out of B.C. mostly because they had the biggest trunk & would give me the gear ratio I wanted & tire/wheel size combo I wanted. Everybody else had only one tire/wheel & gear ratio choice.
Having said that, if I were to do it over, I would go with the RoadSmith kit from The Trike Shop. Not real happy with some aspects of the unit I have, mostly warranty and customer service issues. I do not care for the Motor Trike.

I love the Trike and we have put almost 21K miles on since the build. After a little getting used to, I have no trouble "keeping up". We mostly ride two up in the mountains and I occasionaly find myself "pushing" the other folks. I say check out all the available Kits, find the one you like best and go for it!!!

One tip: If you think you may ever want an Ultimate Seat, get it BEFORE you do the conversion.I didn't and now I can't use one.

If you want some more info about my experience with the Trike, PM me.
Stan