I wouldn't classify my car as a hotrod, but a project noneless. I have had to cut out the entire floor pan of my car. I can't find replacement floorpans and so the only option left is to make one myself.
What brand of car is it? And what body style? You maybe able to find something close or an exact fit that way. An example is nobody makes floor pans for a 55 Pontiac wagon but they do for a 55 Chev, the result, an exact fit. The same goes for Chevelles and Buick Skylarks or a full size Olds and an Impala or a Mercury Comet and a Ford Falcon.
I made the pans for my Henry as none are repopped for it and it was an okay job- not too difficult- just use quality materials (like 18ga. steel) and stiffen with beads or folded seams for strength, then weld them in.