Whatever rim you do choose, get the tallest tire you can clear. Too short of a tire is the biggest downfall to making a new wheel look "right" on an old car. I split mine and went with a 28.5" tall rear tire with 18s and have 17s up front with a 26" tall tire. The 1" smaller rim up front helps the look and I think I'd try to squeak a 255/50 (27" tall) with a little deeper backspace on it next time.
I think you may have a hard time with the 27" tire in the front. With that width I'm not sure that height will work very well, especially if you're lower than stock.
With 275/40/17's on my car in the front now, I'm glad they aren't any taller. They're 26.1" tall tires, and there's no way I could run the inner fender braces as my car is currently set up ( removed them awhile back when I first lowered my car). I also think that, depending on the backspace, you'd run the possibility of more frame interference. Mine clear the frame ok, but I'm all the way out at the fenders with 5" of backspace on my 17x9's. I think with a 27" tall tire I'd be hitting the inside of the fender above the wheel arch with compression, and be right on the frame for turning.
Picture of my current set up with 17x9's and 275/40/17's. All the specs are in the wheel/tire combo thread.