FP has the rear wing kit for $2500
https://performanceparts.ford.com/part/M-17839-FP350S#detailTabSimilar
It's pretty much the APR 71 inch GT250 spec wing (AS-207125) with custom end plates and flap delete. You can get the APR wing for $1400 ish plus the custom end plates (Should be in $200 range shipped if order enough) and take of the flap.
I also found the FP350S's metal sheet hood vent is currently in stock and available to purchase from Dean in Kohn Motorsports while I got my carbon fiber GT4 hood vent from Kohr. The FP one cost $429+shipping and GT4 one cost $880 +shipping plus a week lead time for them to get it from Canada. (Apparently a lot of GT4 parts are from Canada same as the hood)
Also the FP350S's front splitter is no longer available from Capaldi Racing anymore as I was trying to order it last month their manager told me they kind reach the agreement with Ford Performance and from now on FP would be the only place to sell it but FP still hasn't put it online so no place to get it for now. The page on Capaldi Racing was pulled off since then. If anyone is interested in the price Capaldi asked $1250 for the splitter and $220.53 for the pencil Rod kit. I think FP would jack up the price significantly when they become available. I end up with GT4 splitter for $1995, Dive planes $899 and splitter cable $419.30
I have also inquire the brake duct and camber plate from Kohr motorsport. The FP brake duct is not available and the GT4 one made with carbon fiber cost $2000 a set. Dean told me they had never installed the camber plate with Magneride suspension but out of his head it's very doable but you will lose the strut tower brace.
The GT4 rear wing is also available and would cost you $8000 range if you care. It's the same wing used on GT500 with higher stands.