In my area of the country 3/8" is 50% thicker than 1/4" (2/8")!:confused2::confused2:R-enforcing the top lip of your "LA304 loader with 2" X 2" X 3/8" angle" Is going to be not strong enough go with 2x2x1/4" and the 1/4" plate underneath is not a bad idea either.
Steve
Kubota B7800