My tank had just enough slack in the hoses to get at the clamps and get them off,,but I wished there were more...if there isn't you could just cut them off with cutting pliers ,they are probably old and ready to leak anyway..todays ethanol gas likes to melt old hoses!..and make them leak or clog the system up with bits of rubber..
I replace them with new while I have the tank out,it beats trying to do it later!..I have successfully got one hose on the sending unit with the tank installed before,and the clamp tightened,but my hands were bloody after it was fixed..

..there aint much room between the cab and bed..
A brass punch is a great idea..sparks can fly when a steel screwdriver slips on rusty metal..I never have one handy though..so far I haven't blown myself up..you could make a chisel out of copper tubing that would work I guess..
I always cringe when I help a friend change in tank fuel pumps --he chain smokes ,and always has a ciggarette going while he is using a cold chisel to get the lock ring off the sending unit...
I wait FAR away,till he is done--(near the fire extinguisher!),..and needs me to help him hoist the tank back up onto the jack..(its seems fuel pumps always die when the tank is more than 3/4 full when its a big tank!)...he knows better,but has done this and gotten away with it so many times,that no amount of preaching will make him change..so I dont bother with the sermon..

..in a way I think he wishes it WOULD blow up...he has lived thru some bad times..