what size tyre would give a nice stretch on 13x7 wheels?

175/50 would be reasonable but say byebye to any speedo accuracy

Lol yeah,175x50 for low profile stretch,looks great but will reduce the cars gearing considerably,and make speedo and mileometer read fast - form over function.

165x55 would actually give maximum stretch,whilst still looking nearly as low pro and the gearing would be a touch better - never seen a set on,so i dont know how they'd actually look. Or drive. Or even hold air.

185x60 would be best for gearing,but low stretch and not a very low profile - function over form.