Ok on my 66 at the bottom of the kick panel where the floor meats and below that on the inside rocker panel there is a lot of rust. Is the best way to repair this buy cutting away most of the rust and putting sheet metal over it and welding it in place, than paint it and for get about it. I am doing this before I put the new floor panel in seeing how I already cut the old one out. This is the same on bothe left and right side.

I'm helping a buddy to floors and inner rockers on a 65 with the same problem.

We cut up the sill plate and cut the inner rocker out with a saws all.

That's the only way wouthout lifting the body from the frame.

As for the kick panels, you need to remove the vents and clean/por the inner structure. Make good drains so water/trash don't collect and rust from the inside.