KONI's are discontinued for the MN12.
Do this: Tokico's in front, Bilsteins in back, fresh bushing all around. Get as many of the solid bushings from Jay as you can. See this thread
Get the Vogtland springs you mentioned, a 1-1/4" ADDCO bar in the back and call it a day.
There may be other recommendations for front shocks but this will get you a solid performance suspension.
All of this is excellent advice. If you can find them, 89 SC front and rear sway bars are a nice upgrade (unless you go Addco). I am a big fan of chassis bracing. The more solid the chassis is, the more responsive to cornering inputs it will be since it will reduce flex through he metal. Front and rear tower braces, front and rear subframe bracing, etc.
97 Thunderbird LX (The GT Bird)
2003 Explorer WAP block with Modular Head Shop "street ported" heads and Stage 2 PI NA cams, 75mm Accufab throttle body, C&L upper intake plenum, Kooks 1.75" primary/3" collector headers, 2.5" full exhaust with mid mount Magnaflow dual in/out muffler, 24lb/hr injectors, 80mm MAF, Tuning from Don @ www.lasotaracing.com
, CAI that feeds from fenderwell. Jmod, 3.73:1 TL in Mark VIII carrier, Mark VIII aluminum LCAs, 93 Mark VIII driveshaft, PBR brakes (soon to be Cobras), 18x9 wheels with 35mm offset, 255/40/ZR18 Tires, Front and Rear strut/shock bracing, GR-2 shocks, Eibach 1.5" springs, 1989 SC front and rear sway bars.