need some advice
 

Im tryin to change the gas tank in my 1987 cherokee limited, the nuts wont come off!! everytime i crank the wrench the L-bolt moves side to side... i always thought those L-bolts were welded onto the frame but i guess not eh?...im thinking about just cutting them off an was wondering if n e of you guys think i might be able to find new ones at canadian tire or a hardware store

thanx in advance