Thanks 67gta289. Mine is a 65A. Where did you find that info?
In both replies I referenced the MPC, but that might be something you are unfamiliar with. It is the Master Parts Catalog. For many years there were "one year" MPCs, and those were periodically supplanted by multi-year MPCs, such as the 1960-1968 and 1965-1972 versions. The multi-year MPCs are available for purchase. You will see many posts here with a link to a "free" online 1965-1972 version.
Because the MPC intent was for service, it is important to know that (1) not all individual parts were serviced, and (2) similar parts were often combined with other parts in order to reduce variation in inventory, a standard cost reduction practice.
Jeff is right on in mentioning that there are key options that determine springs. In one of the attached MPC pictures you will see a table with check marks. The various combination of options were mapped into a different spring rates and therefore spring part numbers. Those key options are:
(1) body style
(2) engine/displacement
(3) transmission type
(4) steering - manual or power
(5) air conditioning yes/no
(6) thermactor yes/no
(7) GT yes/no (in the case of a 6 cylinder this item is moot)
Also I should mention that if you have a build sheet, that is the ultimate arbiter of what color springs you should have. Attached is an example. I don't have any 67 6 cylinder examples so this is NOT something you should copy for your car.
The last attachment is a small sample of the cross reference chart. Note that the part number and color identification are listed, along with specifications on the spring including number of coils and wire diameter.
The process should be:
1. Find the build sheet if you can. There are several threads that discuss where it might be, and it depends largely on the assembly plant. From there get the color.
2. If you can't find the build sheet, give us the options and we can use the MPC to hone in on what might be right for you car.
3. If you can, from your existing springs count the number of coils, wire diameter, and free length. The free length may not be the same after all of these years, but data is better than nothing.
4. You can ask others here that have a similar car to report back on what they have on theirs.
If you are fortunate, you will get a few pieces of information that come together so you can figure this out.