Think carefully as you lay it out, if areas of the toe board around the pedals are good go below them, most of the repro floors do not have all the little details of the original the same goes with inner cowl panels they are close but not exacts make cuts that remove the rust but enable you to still make a decent weld. Also companies like Eastwood and TIPS make seam sealer products that make the floor watertight (very important if a daily driver).One last consideration is body panels usually look best with a butt weld this is not always necessary with the floor since it is mostly covered you can use lap joints which are much easier to fit and weld. Harbor freight sells small C-clamps about 2-3" of throat if you cut these in half and weld a small piece of steel to the end opposite from the screw you can tack this to the floor and then close the c-clamp against the panel once you are done tacking it in place loosen the clamp and just work it back and forth till it comes loose. I am talking a small weld here maybe a 1/4" is all. These work great where a vice grip can't or won't get.
