We make our own part from 16ga steel, weld in directional screen in the 4 rod throw windows, and make provision to bolt on our custom pickup. The assembly is then Cadmium, not
Zinc, plated. The part is sized so that once everything is assembled you can lay a bead of clear silicone, our sealant of choice, on the gap between the pan and the block all the way around the outside, then with your finger smooth off the excess al the way around, just like caulking tile. If anything leaks once that's set up, it' sthe rear main seal.
Credit for that method goes to Tony at Keith Craft.