Hi Rommel,
I recently bought one of your new CJ-3a rear seat frames. There were two issues with the legs. Where the front leg is flattened and bent the leg is very weak. I added some weld to improve it's strength.
Also the rear leg does not sit 90 degrees to the jeep bed, and so the pins do not insert completely into the floor mounted catches. I chose to grind some of the leg away to improve the fit and to get a more solid connection with the floor mounted catch.
I've not seen an original seat so I cannot make a comparison, but the seat frame seems sturdy enough.
Randy