fbekholden.com

Background"
FB UTE with red motor - HR disk brake front end - Celica 5 speed gearbox
both master cylinders have label - Break cylinder (Disk)
slave cylinder is adjusted fully to almost touching the thrust washer bearing

Problem:
clutch engages as soon as you start lifting from the floor, hard to put into gear, will try to creep forward when stopped (like an auto)

Question:
will the standard clutch master cylinder have more "volume push" than the break cylinder to give me more throw at the slave cylinder ?

No, both cylinders are the same in volume. The only difference is that the brake master cylinder for drum brakes is fitted with a minimum pressure valve in the bottom of the bore. Both disc brake and clutch master cylinders are essentially the same in volume, bore size, and stroke.
I'm assuming you have standard type cylinders in your car. I would be looking at the bore size of the slave cylinder or length and pivot point dimensions of the clutch fork but not before ensuring its been bled properly.