Thanks everyone, I think we have a plan now. My uncle (his truck), was trying to find a cheap way out but as it turns out, the Autometer speedo and gauges he got came with a sending unit that doesn't fit a regular GM tank. It's only a sending unit without a pickup tube. So I talked him into parting with some cash and we ordered a universal tank from Tanks Inc that has a pickup tube and a small hole for the sending unit. It looks like it will fit the situation without major modification.