Torsion bar crossmember install

Yeah I’d leave it alone unless it’s significantly rusty. Maybe wire wheel it a bit and put a coat of POR15 on it before I buttoned it back up.

If I was going to take it out with the floor already removed I’d tack a 1” bar or something across the rockers to reinforce things a little while I replaced the crossmember. Maybe a couple of them. You don’t want stuff moving around when you replace a crossmember.
I hear ya about leaving good enough alone, but I'm really anal when it comes to doing things, I'll have a nice new floor and an old pitted crossmember, it will drive me crazy after doing all that work, especially when all its gonna take is drilling out a few more spot welds, I'll definitely take your advice about doing a little bracing just in case