I added the clutch reduction kit to my 72 last spring. I got the kit from Larry Stock and it made a huge difference.
The shaft that the gas pedal and bell crank mount to does slide out but you will have almost no room to get the clip off the shaft on the clutch bell crank side without at least unbolting the pedal box. Never mind the clips for the linkage to the pedal and the master cylinder. I pulled the gas pedal off when I did mine but don't know if that was necessary.
I didn't have to completely pull the pedal box but I did unbolt it and partially pulled it away from the body. I didn't open the brake lines but I did remove the power brake booster and pulled the clutch master cylinder (had to disconnect the hydraulic line and bleed out the clutch after I put everything back). Also removed the drivers seat to get more room for sliding under the dash.
It was just hard to do this job because there is so little room and you're popping off a ton of little clips. If you're pretty handy, you can do this yourself.
Just take a lot of pictures and pay a lot of attention to how the bell crank was originally installed so you don't put it in backwards and have to do the whole job over.
Made a huge difference to how hard it was to drive my car.
Feel free to reach out if I can be of any help!