I got holes

[madaca]

Well now that I have the truck running good and the brakes working thanks to the help of several of you here on the forums, I now need to slowly start working on the interior and treating the rust. I stripped out the old rubber mats and pads and cleaned out the inside with a broom and vacuum. Must of been a couple of pounds of dirt from the ranch my grandfather used to drive it to. As you can see from the pic below, I have the usual holes in the usual places of the floor. The rest of the floor is solid. I have them on both sides. The picture you are seeing is the side that is the worst. Im on a budget so this is what I have planned until I can get it done right. I want to treat the truck with phosphoric acid because I heard it stops the rust and converts it. Then I will paint it with some stuff that prevents rust and then patch up the holes on the floor with some fiberglass or something. I will then make some patch panels out of sheet metal and treat them as well and then pop rivet them in place and paint it with some black rustoleum or something similar. So who here has done something similar to this as far as making patch panels and pop riveting them in place. Could I get some feedback or some advice. Remember I am on a budget and right now I just want to stop water from getting in the cab and stop the rust. Later when I save up some money I will install all new floor panels and have them welded in. Thanks for any suggestions.