They are not 4xGuard, though similar, I did them from scratch.

This is going from memory, but I bought 2 pieces of 3/16" steel 2"x36".
I cut them in half giving me 4 18" long pieces.
Cut a slope on the back bottom edge, so they tapered up a little bit in the rear making the rear edge 1 1/2 - 1 3/4".
Drilled 2 7/16" holes through each one to bolt into the rear sub frame.
Drilled matching holes through the sub frame.
Drilled a very large hole through the rear of each piece where the shackle connects.
Bolted it all together.

Cost about $14 in steel and another few for the shackles and bolts.