Old Technolgy

This setup was popular in the early sixties (drag racing) as automatic tranmission technology was not as developed as it is today with things like different speed stall convertors, shift kits and trans brakes.

To modify any transmission type, you would have to machine a special input shaft and modify the convertor housing for a equalizer fork just to start.

The 462 C6 main case (convertor housing is unique to the 462).

You would be better served by either pumping up the Twin-Turbo (LINC), Merc-O-Matic or adapt a C6 to an early 430.

CORRECTION-

I see your application is a 1967 462 C6. You are halfway home. You can upgrade the C6 and it is dual range which means it will shift automatically or you can shift it manually.