As you’re probably aware there is a primary & secondary spring on each. There are literally dozens of different springs Ford had available back in the day. The original springs used for each distributor are listed in the Ford Parts book, along with the other distributor parts (different advance slot cams, and so forth). Unfortunately if I remember the Ford Parts book will just give the part number for the different spring, and not specs as far as spring rate, number of coils etc. I’m sure somewhere buried in the Ford engineering files the actual specs of each spring are recorded. I’m away from my parts books, I can look later if you want, I’d need to know the actual distributor I.D. number, but like I said, it will probably just give me the spring part number. Each year Ford Shop manual for the vehicle usually has the distributor “curve” listed, so a person with a distributor machine would be able to check if their distributor is set to factory spec, but of course a modified engine most likely will want a different timing curve. If you look in the distributor section of the shop manual you will see there are many different distributor curves used. And yes, you can often see a big difference between the two springs.
*edited to add - even on a factory performance application, like a 289 HiPo, 427, etc., the Ford engineers were still thinking about warranty considerations, and other compromises. The guys who know how to modify things like the distributor curve, whether by experience or trial & error, or backdoor tips from the factory engineers, were the ones who often ran a little better at the track.