72 Saginaw 3 speed Speedo Drive gear?

[Accelo]

Do you have the original pencil gear (driven gear)?
All the gears, I have seen, on the output shaft have 8T but admittedly that doesn't mean much.

I guessed the tire size and used your given differential ratio (3:73).
This is the combination I came up with.

Differential ratio 3.73
trans shaft gear 8
Trans output gear 22
Assuming 205/75R15 tires
You would require the small gear.

The 1.84" OD gear uses 17 to 22 tooth pencil gears that are .810" OD
The1.76" OD gear uses 22 to 24 tooth pencil gears that are .870" OD.

Cheers