57 Chevy rear spring move?

I've seen people move the rear springs of a 57 Chevy to the inboard of the frame to run wider tires. I know I'll have to move the gas tank and lose the spare tire well. I was told by someone that I would lose some spability in the car moving the center of gravity. I've researched the pocket spring kits, but they're expensive and look very detailed. Anybody done this?