do you have a hydraulic hose place anywhere nearby?
if you are simply trying to get a new fuel supply line from the tank to the mechanical fuel pump you should be able to reproduce the bubble in the line to keep the hose from blowing off with a partial flare or a bead roll tool. the pump probably has a bubble style hose fitting on the inlet similar to a barb but less harsh on the hose, which should be fine with a good quality fuel line attached, such as rubber style fuel injection fuel line and fuel injection fuel hose clamps instead of gear clamps. from there you need to connect to the steel or stainless line on the frame. the problem is that line doesn't have the bubble on it, correct? what about checking with a hydraulic hose shop about getting a partial bubble flare put on the tube? google bubble flare and you will see what I mean and how it looks.
like this
https://www.youtube.com/watch?v=voP3cmakecs
or this tool
https://www.jegs.com/p/Earls/Earls-E...40092/10002/-1
the jegs tool would be a fairly inexpensive way to go and you could do as many lines as you want. I recommend the fuel injection hose and clamps though. better reinforcement in the rubber line and the clamps don't dig into the hose like a gear clamp does. if you use a fitting for anything just make sure the passage through the fitting is at least the same size as the tubing inside diameter. otherwise it becomes a restriction.
dunno if that helps