if it was me doing the fuel lines I would use a piece of rubber fuel line from the tank to the frame ( this just makes life easier if you ever have to take the tank out for any reason), then a steel line to the front, all bent pretty and secured to the frame with clamps (less chance of a leak and potential fire from fuel leaking onto an exhaust pipe or something crazy), then rubber line from the frame to the fuel pump on the engine. that way you don't have to worry about changing it again in a few years. steel line is gonna last a lot longer and withstand the elements and mechanical damages better than rubber (like if you ever lose a u joint, run over something on the road or even just road gravel). it also doesn't tend to sag over time and looks better too, like it was made to be there in the first place. you only need rubber at the flex points. steel line is probably cheaper than rubber anyway.I would also use a good quality fuel line, something with double cotton braids embedded in the rubber. fuel injection fuel line is really good stuff if you have some extra cash. also, I would use a good quality hose clamp, like the ones used on fuel injection hose, way better clamp than just a regular gear clamp. for the vent i would go over to the frame with rubber and then make a u shaped loop with it so the end of the hose is pointing downward at the end, to stop water etc from getting in. then use a vent from a differential, like a stock chevy 4x4 front diff vent from say an s10 or a full size truck. actually i think the s10 has a bigger vent (it is located next to the rad fan shroud on the drivers side if you are going to pick one up from a wreck). it is plastic and has a barbed hose fitting made to push right into the end of the vent hose. like you were saying, use some clamps to keep it tied up where you want it. I would also use a vented fuel cap on the tank, but only if your tank has an anti syphon fitting at the inlet. otherwise you may get a lot of slosh back when you hit the throttle or go over a big speed bump with a full tank aboard (just saying that because your fuel fill hose is pretty short). you don't want fuel inside your box from slosh back coming out of a vented cap. if you use a non vented cap just make sure you have a good sized vent line and end fittings that can let as much air back into the tank as what your maximum fuel flow will be that is leaving the tank, otherwise your engine will starve for fuel. if you find your engine is running out of fuel at high rpm/load conditions you can always add an electric pump inline near the tank to help keep up. make sure to use a large enough fuel delivery line from the tank to the engine. bigger is better. the suction side of the pump needs a larger line than the outlet, especially when you get farther away from the pump. don't forget to add an inline fuel filter as well, somewhere that has easy access and won't make a mess or be a fire hazard every time you have to change it. I believe steel line will flow more than rubber line, steel line has less friction loss than rubber ine does, especially if the steel line is run nice and straight.
just some thoughts,