Actually when I measured some stock removals (including my own from a ghia), I found the stock to be 20.5 or 21. Stock from a P 924 is 1mm higher, with a 924T being 1mm higher than that. stroll on over to
http://924.org/techsection/10suspension.htm and in the tech section under suspension, they list all of the combos that came stock from the factory for the 924/944/968 series (all fit Type 1 rears with no mods AFAIK) I have personally installed 924 bars in my ghia. A bit of a difference. I now have 924Turbo bars that will go in at the next opportunity, since I want it a little stiffer still.
The cool thing is that the 924 and 924 turbo bars are cheap on Eslay (I got mine for $10 per set plus $15 shipping) because no 924/944/968 owners want the "small bars"Model
http://cgi.ebay.com/ebaymotors/porsc...spagenameZWDVW
http://cgi.ebay.com/ebaymotors/87-Po...spagenameZWD1V
http://cgi.ebay.com/ebaymotors/1986-...spagenameZWD1V
BTW the "24" are probably the 23.5mm
Rob