Rear disk conversion issue

You state that it’s a low pedal height. I’m interpreting it that’s when you depress the pedal but it’s at normal height when at rest. Is the brake booster on a bell crank bracket or is it mounted directly to the firewall? Rather than just saying that it needs more volume and recommending a cylinder with a bigger bore, I’m going to ask what vehicle the adapted calipers were made for. You’re closer, but you probably are going to have to match at least the MC more closely to the calipers. Also, what size and type of brake lines do you have on it? My suspicion is it’s probably going to take this type of MC or maybe larger.
Allstar Performance ALL41064 Allstar Performance Brake Master Cylinders | Summit Racing