You didn't state what wheel size he would like to use...
14" (original dia.),
15",
18"(maybe he is trying to clear large disc brakes?),...etc.
It is a bit of a dance, matching up tire and wheel combos to get the fitment on the `66s and `67s. Since these cars have a narrow(er) wheel house, the wheels' backspacing also plays a critical part. I can tell you what I am running on my `66 Belvedere II (same wheel house): a P255/60 mounted on a
15x7 with
4.25" back-spacing. This tire is
27" tall and I have a little less an inch between the outer wheel house/ fender lip and tire. There is a good inch-and-a-half between the inner wheel house and tire. If I had a wheel with 4 3/4" or 5" back-spacing I'm confident I could fit a P275/60. That tire is a good 28" tall.
before buying mine I test fit a P215/70 mounted on a
15x8 wheel with with 4 1/2" back-spacing and could barely get my fingertips between the tire and wheel lip.
The long of the short of it...The less back-spacing in the rim, the less width you can run...this applies to both wheel and tire. The more back-spacing, the wider of each you can run...to the point you run out of room in the wheel well.
Finally, the last wrench to stick in the spokes:
Not all tires are exctly the same width. A Cooper P255 may be a half inch wider than a BFGoodrich P255. You need to find the mfg specs if at all possible...especially if you are trying to push the outer limits of fitment.
Here is a cool site that allows you to play with tire and wheel dimensions. You can even play with two tires side-by-side in the evnt you want to run different sizes front and back.
http://www.rimsntires.com/specs.jsp
Have I helped, or just added to the confusion? :icon_neutral:
