I'll admit I copied this from the T-bird guys, but it helps on all parts.
" All Ford Strut Shocks P/Ns will share the same basic numbers - the center part of the p/n string - Front 18124, Rear 18125. The first 4 digits indicate the year and product line. The suffix (in this case AA, BA) indicate the revision level.
Here is a breakdown for 5W4Z18124DA:
First 5 = 2005 - Part originally designed for a 2005 Model Year Vehicle
W4 = DEW98 Platform (i.e., = Lincoln LS - RWD Thunderbird is W6)
Z = Ford Customer Service Division Product Analysis (replacement part)
18124 = Basic P/N for a front strut shock
DA = Design / revision level (as I recall the standard struts for the 2005 LS are AA)
Ford definitely shares parts between models. The P/Ns will reflect the original usage."
I just went through last week and mined all the LS sport shocks I could find all the way back. As long as they cross to the 2nd thru 9th characters (xW4Z18124 DA)they will work.
However what you will find as your frustration shows the only sport shocks available are ASH-355 and ASH-357 which are OUT OF PRODUCTION! I sourced mine from 3 different sources to get all four. Both Tasca and Fordpartsgiant could not fill an order. Good luck! and Happy hunting.