I started this project on Sunday morning when all the hardware store were closed. The whole project cost about $10.00 plus stuff I had laying around. I took two L brackets and hammered them flat. I would have used already flat pieces there had been a store open. I bent the pieces about 1 " from the end at the angle shown below. I also drilled an extra hole on the short end and on the long end.



I had 2 pieces of 1X11X1/8 inch steel from a previous project so I drilled those to match the holes in the brackets. I mounted the brackets to the fender with self tapping sheet metal screws. Then I put the passenger seat back on. I had to push it back as far as it would go to get clearance for the brackets. The front seat bolt is on my windowsill but the seat is secure without it. I bolted the steel supports to the brackets by pushing the rear seat cushion in and adding the washers and nut. I also added some hard self stick fabric on the seat front to protect it from the bolts.

At this point the brackets were not perpendicular with the new back rest. I had to use the vise grips and twist them straight.

You can make the back any size that you like. I made mine with a 12 inch piece of 2X8. I ripped some 1X to 2 inches and tacked that to the sides and top. This allowed for the brackets to be hidden.



I stuffed and covered the board with Wallyworld fabric and used a glue gun to fasten it. The back is a piece of 1/8 inch plywood painted black.



I have added 2 pics for reference.





This winter I will probably try to make the brackets all one piece for strength. The only problem will be twisting the steel to get it straight with the back rest. I have a local steel place that works on small jobs cheap.