The 74 has swinging pedals,doesn't it? (mounted under the dash rather than coming up thru the floor).
As long as you have swinging pedals, a master cylinder and bracketry from a 76-86 CJ should be adaptable. The power booster uses a bracket that spaces it out away from the firewall. I've heard the early (pre '74 ?) Wagoneers are the same also.
For top of the line stuff go to www.mpbrakes.com
Bob
tufcj