Ok I am currently running 225/60R/15s on my 87 convertable GT. I have the ugly turbine wheels. I am looking to get new wheels and tires. I'd like to get either 16 or 17 inch wheels and i'd like to get somewhere between a 255 to 295 under the back? anyone know what kind of back spacing or offset I would need? and what kind of mods am I looking at to accomplish this? also another issue is I still have the four lug rear end, should i switch to a five lug? if so why?