SPARE TIRE WELL OR NOT

My spare tire well on my 67 barracuda is rusted out. Bad I have a replacement for it. I got to thinking maybe i will eliminate the spare tire well but how is that going to effect the gas tank. ok Well maybe i will put in an aftermarket tank in. Has anyone done this ?
Well you know the old saying it is better to have it and not need it than to need it and not have it just a thought
Joe