You don’t have go the dream bracing route. You just need to weld on some pieces to keep the body from shifting when you start removing body panels.
In my picture you can see I just welded some leftover pieces of metal to the body to make it more rigid.
I welded my pieces on top because I wanted to be able to work on the bottom without anything getting in the way. You can’t see it in the picture but I welded a piece across the bottom of the rear floor too.
Take measurements from the mounting holes to the cross members and record it making a sort of diagram, then refer to it when you add the new floors.
I would not cut all the floors out at once. Remove them and replace things in phases and measure after each piece. My two cents.
45' MB, ??' MBT, 47' CJ2A, 48' CJ2A,
51' M38#1, 51' M38 #2, 51' M100,
52' M37, ??' M101A1 (1st Gulf War Vet),
53' M38A1, 53' M211, 67' M416,
?? MB / CJ Franken Jeep