Check your rule book first. I can’t remember how much of that you can take out before you need more bars.
I know when I had to make a foot box for my car it was a giant PITA because I never planned for it and getting enough bars to keep the rules freaks happy was hard to do.
I have to add a rocker bar I believe it's called but I will be adding that anyways because of my more than 1 sq foot of floor being replaced.
I'll also be welding a flange to tie what I can of the firewall to the front frame rails and tying the floor into that as well.
Edit, a square foot of firewall modification only requires a dash or lower front window bar.
Rocker bar is for a modified floor