Hello everybody, from Brazil!
I noticed you are looking for a system for sequential gearboxes T1. I manufacture (in handmade scale) this system.

I developed it for use on a motorcycle that I built using engine and gearbox VW T1. But I decided to build more sequential systems due to high demand I had in Brazil. I have sold many units, and one of them I just sell to Mr. J.D. Curry in the USA that will use it in your beetle drag car. Watch my video on YouTube.

https://www.youtube.com/watch?v=9nHtlcfQ4D4

Thank you for accepting me in your group, excuse my English!

Hello Luis, Interesting.  It will be interesting to hear what Mr JD Curry has to say about the use in a buggy.