Ahh, yeah the solid part of the fuel line that sticks up is actually part of the fuel supply line, and not the rail itself. This pic shows it fairly well, right in line with the intake ports and thermostat housing (which might also be an obstacle):
I can see how you'd want to change that to make supercharger installation easier, but I'd want to measure and check to see clearance on the thermostat housing/upper radiator hose too. No reason to bother with fuel supply line/rails if the thermostat/radiator hose are going to be an issue you can't easily do anything about. You may indeed be better off offsetting the charger than messing with the time and money needed to resolve both of those hurdles.
Is your truck flex fuel or standard? AFAIK, the standard Vulcan had 19lb injectors and the flex fuel had 24lb injectors. If your truck is standard fuel, the flex fuel options should be an easy plug and play solution (assuming you get a proper tune). The 1.8's and other stuff
might be helped with larger injectors, and a subsequent tune but it's probably not required. It would be less money to keep the stock injectors/tune if you're just running the 1.8 rollers, and save the other upgrades for when you add boost and they're truly needed.