Hi si74 the easiest way to do your floor would be to treat what surface rust there is and prime it,then coat over all the existing ford underseal in sprayable stone guard witch is over paintable , then paint it,if you are going to go through all the trouble of painting it in the first place then do it once and do it right,take off all the suspension,fuel lines brake pipes etc,start with a fresh canvas,paint into all the nooks and crannys,then powder coat or paint the suspension etc and refit,job done properly,and not wishing you had done things differently,hope this helps regards paul