[luvbowties]

Hi, Bret.
If you find your diff. is 63 1/2": (Cap Fab correctly stated this dimension.)
7-inch rallys will clear with max size of 235-75-15 w/a lowered rear....I just confirmed it about 6 PM tonite on my 66 w/63 1/2" diff. I couldn't use my 265-60-15's on ANY wheel! Your 8 inchers MAY clear w/the 235-75-15??? May go "some" wider w/stock height. GM made rally's in 8", 7", and I believe 6.5's. The 6.5's(?) look kinda wimpy imho.

If you use a 65'ish rear end:
(I think your years are correct: 65-69. Maybe even a 64?)and get a set of 5-lug rallys that are 7 inches wide, you should be able to use 235-75-15, or a tad wider, IF rear has been lowered significantly. If rear is at stock height the 8 inch x 5 lugs should work & may accept bigger/wider tires than 235-75's.

Should you use the older rear w/6 lugs, pull your axles & take them along with drums to a machine shop. They can re-drill flanges & drums to accept the "newer" 5 luggers. Have to plug only one of the 6 holes, as 4 will locate on 'virgin' metal; that 5th one drills into an original of the 6 holes. While there, ensure the drum you take them fits over the 'register meat'(the stick-out ridge on axle-flange that centers the brake drum's center hole); else the m/shop has to cut ridge down to match--like if you find a '71 drum w/5 holes already: its centering hole is smaller than the 6-lug's. Also don't let the fins on a 71 drum fool you into thinking they are wider: brake surface is same as 65.



Good luck & have fun.
sam