Whats the Correct setup for the 67 big block w/ 4 speed Muncie (4.56 gear) on the Speedo Cable???

*Length??
*2 piece or 1 piece???
*Speedo Reduction Adapter (Ratio?)

I'm trying to keep it mostly original.

Just found out through Ricks Camaro parts that a 1pc 73" is what they recommended.

Anyone out there know about Speedo reduction for 4.11 -4.56 gear ratio's??