K5 tank install in 77 c10

[sinisterfist]

I have the tank mounted all my lines ran. Im down to plumbing a filler neck I've searched high and low and cannot seem to find any real info on what to use for the filler neck. The search function is not working on here. And it seems ai clouds anything I try to search relating to getting answers. If any body has some helpful information or pictures on what they did that would be awesome. Its a 77 c10 shortbed fleet side ill add pictures later.