1/2" Fuel Line Gas Tank?

['70 C/10 SS500]

I've heard that BB equipped trucks came with 1/2" fuel lines. I suppose then that the fittings on the gas tank would be 1/2" as well. I'm getting ready to do a complete overhaul of my fuel system because my truck was originally I6-250 powered. The 5/16" fuel lines trying to feed my swapped 500cid Caddy motor are too small IMO, and I'm going to go bigger. My questions are:

1. Is it true that I6 vs. BB truck's gas tanks have different sized FITTINGS for the fuel line coming out of them? If yes, I'd hate to re-use my old tank and have a small 5/16" outlet trying to feed 1/2" lines from a transition just outside the tank. Sounds kind of silly to have any choke point at all if I'm going through all this trouble, gotta get rid of ALL the old 5/16" stuff!

2. If question #1 is true, then where, other than the wrecking yards, can I find a BB / 1/2" fuel line gas tank? Are they available new?

3. Are the return lines different depending on size of motor, or all they all 5/16"?

I just thought about this....When I say fittings or outlet, I guess that is in actuality the Sending Unit, right? That is the pickup point for fuel to leave the gas tank right? So, are there different sized sending units?

I'm sure this will all be cleared up quick, enough rambling and nose bleeding!
Please give some input to clear some of this up for me, thanks!