new floor pans

bought new floor pans for 78 trans am but they do not sit perfect...what can be done to get them to sit perfect...and if you have had exp. with putting them in give me as much info as possible

well cut the old ones out then leave about an inch metal on the whole edge of the old pans then set the new pans in and mark where they dont fit quite right then cut the edges and set them in and hammer them down flat to get a good fit and clean the old metal so you see bare metal and do the same to the new pans then once you've done that then tack weld them in and after that when you are happy with the placement of the new pans then lay a good smooth bead down over the whole edge of the pans as well as the old metal then seal the top edges of the metal with seam sealer and prime and paint the bottom of the welded area on the under side of the car i hope this helps you out