Best Jackshaft kit?

[Brian1A]

I would like to install a jack shaft /shift kit. Question's : What is the best one ? Will they fit my Trek 21 spd? Never installed one, is it pretty simple.
Thanks!!

 

[MotorBicycleRacing]

I would like to install a jack shaft /shift kit. Question's : What is the best one ? Will they fit my Trek 21 spd? Never installed one, is it pretty simple.
Thanks!!

www.sickbikeparts.com is the only one worth buying.
There is an installation guide on there.