Another Fuel Tank and Fuel Line Question

Assuming they're not foamed in. Poke holes in the end of the hose and thread a piece of safety wire through that and the end of the new hose and pull through. Where are you and do you have a tank fabricator? I'm picking one up from Atlantic Coastal Welding in Jersey. They do great work.

Classic Mako has some photo records of a whole bunch of tank changes. They are a great resource when planning a project.

Is your tank itself damaged? Seems like a lot of work to replace if you could just give it a good cleaning and replace the lines. The lines are usually where the "gunk" comes from which clogs filters and injectors.

I replaced my vent hoses about 4 or 5 years ago and the only trouble was with the auxiliary.
Since you said hose I'm assuming you only have a main tank.
I didn't have much trouble getting the vent hose on main but had to cut out and install an access plate to get aux. vent hose in. The outside diameter of the new vent hose was larger than the one replaced and it wouldn't fit through the hole drilled at the factory.
I also nicked the aux fuel filler hose but I though it was fine until last trip and smelled fuel . After checking I found a small leak so I replaced it this weekend. . It was a PIA for me!
I'm not sure about the layout of your Grady but my main vent hose was much easier than aux.and I think the filler will be easier also.
I can say it took 9 ft of filler hose for the aux.tank.