fenders need to be wider?

[la hi]

I have a 57 swb and I put a 95 camaro rear end with disc brakes, posi-traction. My bed will not fit as the new set up is to wide and the tires will not fit under the fenders.
I have removed the fenders and I need 1&1/2 to 2 inches more room on each fender to have a good fit.
The welding shop recommends that i cut the fender in half and weld a strip into the middle when I determine the correct size of expansion needed.
My other options are wheel offset, or narrower tires and I am not sure that will work. (trying out rim's till I find one that fits) I have 15" rally 5 bolt rims all around.
Any ideas??