Fabricating new seat mounts..

Are there any metal fabricators out there in FABO land ?

I am installing non mopar buckets in our '75 Duster.

They are 20 inches wide at the front so I know they fit. Unfortunately, the track is 18 inches wide (Duster tracks are 12 inches hole to hole) so I am looking at the following situation:



I don't weld so all will have to be held together by nuts and bolts.

Probably the best product to use would be channel or box steel but I am trying to keep the height down. can I use lets say 1/8 or 3/16 cold finished rolled steel or would that make the seats too springy ?

Advice or what have you done ?

Thanks
Grassy