The install time for a speedo gear for someone who knows what they're doing is about 10 minutes... (much less than installing a speedcal)
My recommendation is to spend the 50-60 dollar larbor charge in your area and the 15 dollar speedo gear.
Its cheaper, and you're not messing with electronics....
Speedos the better way to go, but if you want the speedcal, be my guest....

__________________
Uncle Sam
"What the hell is up with all the gauges?
Calling Captain Kirk, your ride awaits... Phasers on stun...."