filler options
If you want a metal type look, then an all metal type product would be fine, otherwise I would recommend using the Evercoat line. I recommend Rage filler it works down well with 80 grit and finishes well with 180. Then 2 coats of Slick Sand and your ready to block and final sand for paint. I would use duraglass if there were any areas in the weld that may be pin holed or lower than 1/8 inch