i had 255/50/16's on GTA rims front and rear on my 71, and only the one rear wheelwell that had a dent rubbed a little bit.
the 255/60/15's i had on a set of 15X7 Z/28 rims fit like they were made for the car. i had 235/60/15's on the front with the Z rims, and it looked badass..
You really need to measure before you buy rims and tires. There is enough variation in these cars that just cause a wheel/tire combo fits one guys car doesnt mean it will fit your car. About the only size of wheel/tire that you can be confident will fit without measuing is the stock size.
Also some guys are willing to put up with things you may not be..ie rolling the wheel lip, slight rubbing on bumps, not being able to use the back seat or the tires rub, etc, etc....So you really need to mock it up and measure it out. IMO rims and tires are too expensive to have to buy them more then once cause they dont fit like you thought they would since "Billy Bob" told ya they should work.
Measure twice and buy once is a good rule for tires/rims.
When I was looking at tires for my Camaro, I made a cardboard template with the correct backspacing I needed and checked for fit at every angle I could. You'll have to convert metric to standard 25.4mm = 1" so a 275/60/15 comes out to be approx 28" tall x 10.8"wide.
275/25.4 = 10.8 wide
10.8 x .6= 6.49
6.49 x 2 = 13.0
13.0 + 15 = 28 tall
*275 is mm wide (overall)
*60 is aspect (sidewall, one side) need to times by 2 for top and bottom of tire ( the .6 above) if it was a 50 it would be .5, if it was a 45 it would be .45, get the picture ?
*15 is the wheel diameter, so add 15, if it's a 16,17,18, ect, then add that number.
I have seen somewhere on the net, but I cant find it now, where a guy used a peice of angle bolted to his hub to represent the dia of the wheel combo he wanted and then rotated that around to various spots and took meansuments from that. He was able to get the proper back space and figure out exactly the widest tire he could use. it appeared to work well. He said one thing to remember when doing this is that the angle isnt sitting in the exact position the rim would do to the centering hub on the axle that the drum and rim ride on. You have to take that into account when you measure.
Anyway good luck with getting new rims and tires...lets see some pics when your done.
Ya night shades trick is simular to what i was describing in my post except that he used wood and I was talking about using angle....it is the same process however....very good way to tell the exact amount of space you have and how much backspace you will need too. Win win situation IMO :beers: