G-force transmissions has three different ones. Has anyone used any of them?

He has Spur Dog Ring, Helical Dog Ring, and Helical Synchronized.

What's the difference? The guy said the Dog stuff was for racing mainly, but could be driven on the street. Would it be wise to learn about racing gears like this? I figure to use my car to do autocross, and take driver's schools at road courses.

Here's the website:

http://www.gforcetransmissions.com