Thanks DD, looks like a good approach.

Been doing more digging. For the sake of posterity and anyone stumbling across this thread in the future I'll post what I found and where I netted out. I'm reasonably sure this is correct, though with most of the available catalogs I've found being printed in German, it's a challenge. Also, there's the assumption that the German market = USA offerings..no way for me to know.

It seems when Specialized introduced suspension forks 1992 or 1993 (I don't have a 1992 catalog, there were no hardtails in the 1991 catalog and they do exist in the 93 catalog) they had the standard-previous Stumpy frames(fork A2C of 394mm) and they had the FS models. The FS models were basically "suspension fork ready" frames. The FS models were offered as rigid bikes as well as hardtails with a suspension fork. The rigid FS models had a suspension corrected fork with an A2C of 410mm. That number varied in the references (various forums) between 406 and 413...for the sake of a short quarter inch..we'll call it 410mm. The Mag21 (or Judy?) suspension forks offered on the FS had two travel lengths, 48 and 63mm. The 63mm travel fork had a 420mm A2C unloaded. Fork rakes for all models were listed as 42mm in a 1996 catalog I located.

The above is correct as far as I can tell so far. If anyone has better info feel free to pop in..

DD's..."I'd start with identifying the year of the frame and then figuring out the fork it came with and deriving the A-C from that." would be the way to go..thx..

As far as how much does varying the A2C from a frame's original spec impact handling...that seems to be a topic that has been discussed in many places at length. I netted out that if the replacement fork is within 20-25mm of the original A2C spec, then things should be ok. Rake(offset) should also be within 3-5mm(??) of original spec. There's always some folks that say the A2C variation must be minimal and others that run a fork at +50mm from spec and they say handling is great. Such are opinions on forums..