OK now I've got some insight. I'm thinking I may have an option here. I have the pan and pickup from the 318 Magnum that I tore down. I wonder if I can use it in the early trucks. It looks a little deeper but the shape is basically the same. I'd have to clean it out real good (flood motor, but still oily) but its very usable.

Another option that I was thinking was cutting the front end rail rubber gasket up and filling those gaps that way and with a bit of silicone for good measure. But it looks like the gasket is going to be $28-something at the parts store so it may wait until spring.