Need help with tire sizes please

[toupee]

Hi all,

I just made a deal on a 71 Roadrunner.  The car has 15" rallye wheels on it and 235/60R15 tires.  I don't like the the "skinny" look of the rear tires  or the level stance of the car at the moment.  Looking for opinions on what my best choice would be on replacing the back tires with something wider and taller to give the car an aggressive stance and maybe fill up the wheel wells more.  I'm on a budget so I'm trying to stick with the rallyes that are on the car and would rather not replace the rims.
Thanks!

[suntech]

295/50 x 15, on 10 wide rims should do it 4,5 / 5 inch of backspace.