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?

[GriffGirl]

I don't actually have ABS, although I don't think it would be any harder than without ABS. I imagine you would use the sensors that are on your car already. They actually detect wheel speed, so it stands to reason that they control the application of the brake regardless of being drum or disc. However, I don't know this for a fact. It could also be that ABS on an ST only has wheel speed sensors on the front wheels, since that's where the majority of your braking load is anyway. Do GTs have wheel speed sensors on all 4 wheels? It seems like I read on here they do. . . IDK.