It might be worth a little more than other Twister II Mustangs, but since the Twister II was just a trim option, with no performance parts, it would take a real Mustang fan to pay much extra, I would think. Hot Rod had a good article on them, including this:
"Such an exciting product inspired memories of the marque's many special editions. Someone in Ford's Kansas City sales district noticed that 1985 marked the 15th anniversary of the Twister Special. Collaborating with Ford again, dealers arranged to purchase 90 GTs in hatchback and convertible form and apply certain commemorative decals as part of a "Twister II" promotion.
Because it was a cosmetic package that required no active factory involvement, dealers were free to order the cars with any combination of colors, powerplants, and options normally available on the GT. The Twister II featured on these pages, for example, is wearing stock GT 10-spoke wheels wrapped with Goodyear Gatorback rubber; the hatch louvers and T-top roof were both extra-cost options.
According to research undertaken by David and Kathy Bowers at MustangGT.org, Twister II GTs were assembled in October 1984 with vehicle identification numbers falling somewhere between 109800-109899, 110300-110399, and 112200-112299. The majority were painted Jalapeo Red (code 2R), but Oxford White (9L), Medium Canyon Red Metallic (2A), and possibly Silver Metallic (1E) were also offered.
Along with the rocker panel "TWISTER II" striping and "tornado with eyes" funnel cloud insignia, the package included a bronze dashplate, an alabaster coaster with a running horse logo, and "1985 Limited Edition TWISTER II, Kansas City District, October 1984" lettering, and a press kit from Ford discussing the promotion. Unfortunately, not all Twister IIs received dashplates, coasters, and press kits, as some were taken by sales staff members with sticky fingers.
All Twister IIs have a DSO of 53 (Kansas City) on their certification label and buildsheet, but the Ford window sticker doesn't mention anything about the package. According to research, 74 Twister IIs were five-speed hatchbacks, 2 were automatic-equipped hatchbacks, 9 were five-speed convertibles, and 5 were automatic convertibles. A dozen or so Twister IIs were ordered with the optional 3.08:1 rear-axle gears, but no convertibles were so equipped."