I am looking at the same situation for my '62 C-10 with tank in the cab. The issues for me are more complex, because my conversion is fuel injected. But here are the issues I found which may be appliable to you;
1. I have to move the filler neck, and do body work on the cab, or keep the filler neck as is and somehow run a new filler line out of the cab, along the frame, and into the new tank under the bed. If I put a new filler neck in, which is not in the cab, where shall I put it if I don't want it sticking out of the bed.
2. What do I do with my spare tire.
3. Since I've increased the distance to the tank, I think I need at least a 3/8" line, which isn't there now. I think braided stainless steel fuel line is the answer there.
4. How do I propery vent the new tank.
5. I will need a new gauge sending unit that is compatible ohm wise with my dash gauge.
6. Will your mechanical fuel pump be strong enough to pull the distance.
Since you are not going fuel injected, LMC may have some of these answers for you, or call Rock Valley Custom Tanks at 18003441934.
