Master Cylinder - 1/2 vs 3/4

[TugOwar]

Sup people,

I'm wondering if there is any difference between a 1/2 master cylinder and a 3/4 ton master cylinder for our year models. I've looked at the 1/2 and everything is exactly the same EXCEPT the diameter of the base that fits into the booster - slightly smaller diameter on the 1/2. The depth where the rod slides into the piston of the MC is even the same.

Why won't 1/2 work in place of a 3/4?

All the parts places in town stock the 1/2 but have to order the 3/4. Granted, it's only a 1 day wait but I'm impatient!