I upgraded the booster and master cyl on my ke25 years ago.
not for the same reason as you are tho. I changed it because the original non boosted single circuit system was totally inadequate and I couldnt get it to operate properly. not to metion dangerous.
I used a 180B booster and skyline master cyl. The benefit of the 180B booster is that it is compact and common (at the time 1995). it was not a bolt in swap but wasnt to hard.
need to drill four holes in firewall and add a few extra brake lines etc.