I was thinking about that too. Just didn't know if welding in little patch's would move the floor around and then become difficult to connect to the new frame. It definitely would be easier to access the floorpan without the frame in the way.
I have just about everything for the new frame. Fuel lines, brake lines, front and rear suspension, disc brakes, dropped spindles, etc. Installing all that would give me time to fix the floorboards before sitting it back down on the frame.
1968 Impala SS Fastback 383 stroker