Welcome.
You’re in luck living in Western WA. There are a lot of good parts around. Just gotta find them.
Personally and especially since you’re on a budget, you could find virtually all of the parts, used.
But I’d consider getting the switch and the valve new. And likely the tank. Unless you find a tank that is in good shape. They’re out there too.
Hangar brackets, tank straps, filler snout find used ones.
Search CL and FB. There are a few people who part out these trucks as a side hustle. And there’s always people just selling random parts and parts trucks.
Good news is you don’t need that stuff right away if you still have to paint the truck, so you have time to find used stuff for cheap.
And if you don’t add the tank, just dummy it up after painting. Way easier than the bodywork to get rid of the opening.