As some one who has recently reworked the brake system on my 46 to have disc brakes and a modern master with booster I can tell you that it take a lot of time to make something that works. I probably have a 150 hours in making mine work correctly. Now, it stops extremely well and I drive it in stop and go traffic.
Find a source for the hydrovac and send it in for repair. Even at $500 repair would be much cheaper and easier than adapting something else. Now if you want it to work better that is a different story!
My disc brake thread...
https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=708681#Post708681Good luck which ever way you choose to go!
