master cylinder?

Since already plumbed, I would just run it and see how it feels. The extra fluid capacity is for original owners who would neglect maintenance. If you check the level every 1-2 years, you should be fine. I wonder if the factory set the fluid capacity to match wearing the pads down to the steel.

If really worried, install a modern MC like I did (see avatar) to get a "fluid low" warning switch. I haven't figured how or if I will wire it to the dash. I regularly check fluids in all my cars anyway.