I need two sheets of metal one 20" by 17 and one 20" by 12". its for a truck floorboared im not sure what type or size of metal i should use for this. Any help? prices?

 

I'm going to assume it's for a 73-79 dent so why don't you just buy floorboards. You can also get some used body panels from a scrap yard, if you must have new flat stock call a supplier in your area 18-20ga should be fine. I called the one I use but they were closed. Look here Flashback F100's - USA Made Steel Made Repair Panels*On This page will be only USA Made Repair Panels,, not like others that carry those Black Tawain cheap repair panels. nice floorboards are $60. per side.

 

For that floor pan does it go under the seat cause the metal there is perfectly fine. I just need from the seet to the fire wall area

 

I don't think they are that long but the idea is to use what you need, your going to remove rusted material until you get to solid floor that you can weld to then trim the new panel to fit while keeping it as neat as you can.