I run a clutch type sure grip for HSAX and it works quite well. Probably similar to your '68 unit. They can be set up with various levels of "tightness". Mine is "medium". Full tight might be good on a drag car but not a handling car per my understanding. Too tight can upset the car on corner exit.

The worm gear type are great in theory... but 8.75" versions have suffered quality problems and noise.

I would suggest clutch type.