Soft brakes after changing wheel cylinders.

yepperz!!!! NOW that you have a NEWLY closed system again....and your MC is meeting with Proper and full hydraulic pressure...NOW the MC shows itself as yet another in a
"string " of problems.
Brakes for me are kinda like a game of domino's...you touch any part of them and you might as well just replace everything....ESPECIALLY if the parts are all over 20 years old...lines can last a wee bit longer like maybe up to 30 IF they do not see ANY weather or if they are stainless......stainless can go to 40 but after that it is best to replace everything wheel cyls, rubber lines, steel lines and MC......I may go a lil over board BUT I want to make sure the car I gave all that money building, STOPS when I tell it to...EVERYTIME. just my thought/2 cents