plate steel works very well, won't crack, and doesn't deform like aluminum. Find your local metal supplier, they'll have what you need in the right width/length. The only issue, the center pin on the stock leaf may not be high enough to reach the perch of the rear end after the block is in place. The perch is recessed so you have room to work, my suggestion, weld a ring on the block to surround the current pin, then weld a pin on top of that ring to seat in the perch. Or, replace the stock pin with a longer one.