Floor pan Repair Type 3 squareback

just picked up a square back and needs some floor pan fire wall rust cut out, and same with the boot near the engine bay..

just wondering if its best to cut out the whole area of the rust or just where the holes have formed.

i was just thinking of laying new sheet metal down..
not sure
please help

I got a donor body last week which i bought for the inner guards and they turned out to be no good. So I have whole body in pieces and very little that i can use for myself.

What year is yours and can you post pics so I know which bits exactly and I should be able to help out.