skinny floor rails

I bought a set of new floor rails and a drivers side replacement floor from a site a while ago and have just got the floor welded in. I have gone to fit the floor support rails and noticed they are about 3mm narrower than the rails on my 73 240z. If they didn't have the folded mounting section I could slide them up inside my old rails. Bummer.

I don't want it to look like they are tacked on to the old rails so I'm going to have to get some new ones made locally. Anyone else had this problem?