Convertible floor pan replacement

Rule #1 is cut the offending metal out first.

Then drill out all spotwelds till you have good metal to weld to.

The torsion bar x member, the front frame rails, the rockers all need to be clean for you to attach the new floor pan to.

As for bracing, yes, yes and yes.

Also neasure, measure, measure.

You might want to build a jig of sorts to hold the body on while you are removing and replacing.

There are many threads here but i cant say i have seen a step by step how to.

Are you planning on an entire floor or just patches?

Post some photos of what you are starting with.

Best of luck to you.