[Irish1941]

Floors are not easy to do on '73-'75. I'm sure the entire rocker box is rotten as well if the floor is gone. That means cab mounts as well. Those yrs were recycled steel and they rust just looking at them.
Take the roof off as is and the doors won't close.
Take your time in figuring what you need to do. I could write it up a how-to but it'd take me a day. I will tell you this before you start:
Make a bar that goes from 1/4 to 1/4 behind the front seats and ties the sides together and make for both door jambs as well.
start cutting without and nothing will line up again. If you have a body shop friend, good time to ask how to proceed.