Were Rally I wheels available on birds in 68?

Also are 15" wheels needed to accomodate disc brakes? Does 4 or 4 1/2" backspacing matter?

i'm pretty sure the rally II was not available in 68, but the rally I was. but the rally I was only available in 14".

as far as disc brakes, a 14" will fit, as long as it is not a drum only rim. i think all raly I rims will work with disc.

hopefully someone will correct me if i'm wrong. the year one cataloge i once had explained much of this, but i no longer have it.

Rally ones came available in 1967. Rally one wheels were available up to 1968. Both were only in 14 inch wheels.
15 in Rally 2 wheels came in 1972, I think

Crap
That should read Rally 2's became available in 1967

what do you mean by the 4 or 4 1/2 inch back spacing? i'm not clear on that. is it the spacing of the wheel from the hub?

back spacing is mesured from the back of the rim to the mounting flange.

a 6" rim with 4 1/2" backspacing would set inward 1/2" more than one with 4" backspacing, and would only leave 1 1/2" from the mounting flange to the outside of the rim instead of 2".

i guess this might be the difference on some rims whether they fit disc brakes or not?

As far as Rally II 14" rims I've seen 6 7 and 8" for sale. Anyone know which of these widths were offered in 68? Also which will or won't work with disc brakes?
It sounds like the smaller the backspacing the more room there would be for disc brakes maybe?

Go to www.pontiacserver.com/wheels.html
This will give you pretty much anything you want to know about the Firebird rims. ie size, code #.
Good luck and I hope this helps.