Bench to bucket conversion

Talk about a fast reply! Thanks guys :) Are these support plates just a piece of square steel(that I could easily cut and make) under each corner, or are they a factory specific piece?
Edit: Ive found these online and it looks pretty easy just to fab some up, do they need to be welded in place, or can they be placed loose under the seat tracks?
https://www.rosevillemoparts.com/product/bucket-seat-floor-brackets-67-76-dodge-plymouth-a-body/