When I replaced my fuel pump I disconnected the lines there . I don`t know if you can drop the tank far enough as the lines are plastic I would`nt risk pulling them too far. As for welding I`ve been cleaning & rust treating my chassis ready to put the recon box back. The only bit I have to patch up is an outrigger where the side steps attach, so pretty pleased for an o4 disco as the rest looks good so far.
Dan