Actually the C mod has a four speed transaxle with dogs instead of synchros allowing shifts without touching the clutch. The clutch is needed only for takeoff. The shift is as quick as the blink of an eye.

I did once have a 66 corvair with the powerslide....very poor combination.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.