Rear drum to disc conversion question, Do I need to do anything with the master cylinder? Options

[GriffGirl]

Someone told me he thought I will need to do something with/replace my master cylinder when I convert my rear drum brakes to disc brakes; something about the proportioning valve.

Here's what he said:

In regard to your brake swap, I could be wrong, but I'm almost positive that you'll need a different proportioning valve...When you do it, though, you should see about swapping the proportioning valve and
master cylinder (if it's different on the GTs)... Drum brake wheel cylinders and disc brake calipers use different amounts of fluid (typically) and if you swap from the former to the latter, your rear discs brakes won't be doing as much work as they should.

This is all greek to me. Help? Is this something I should look further in to?

[alltracman78]

That's pretty much how it works.

The P valve only allows a certain bit of pressure to the rears.
Too much pressure and the rear wheels will lock up.
Drum brakes get less pressure than disc brakes, and also get the pressure first [drums have to move further to start working] so ideally you want to replace the P valve when you add the discs.

I'm not sure if the master cylinder is different as well, or the same.
I do know on the 5 th gens the ABS cars have a slightly larger MC, so it's a bit of an upgrade for those that don't have it.