Proportioning Valve

I have a '66 Cuda with '73 disks.
It's been running around with NO proportioning valve for years with no problems.

In fact, we did a Ford 8.8 swap with rear disks and it STILL stops fine using the original '73 manual master cyl.
And this is a street car that gets strip time, so it is driven hard and stopped hard and it has never once acted like it wanted to lock the rear prematurely or anything.

Remember, the prop valve is really there to turn on the Brake light as a warning of a hydraulic failure, and you dont have a light to hook it to on a '65, so why do you need the valve??