Not sure of your budget but you can get an entire floor pan for $450 with free shipping. If you only had a few holes I would say just patch them up and call it a day, but it seems you have more then a few and the floor is prolly pretty weak. If you dont care about looks you could just cut out the rust and weld in some sheet metal, thats what I did since its a floor and nobody will see it under the carpet.
Here is the entire floor pan, its cheaper to get the entire thing then it is to buy halfs and have to pay for shipping.
http://www.gbodyparts.com/product_in...oducts_id=1484