Hi,
I drag raced, road raced and street drove a Soft Lok clutch with 4.10 rear gears and a GM 3550 starting in 1993.. The Tremec 3550 was the base model I modified to become the first GM Tremec. The TKO-500 & TKO-600 replaced my GM 3550 (and GM TKO) model I developed and marketed before Tremec released their GM TKO models.