These were Koni single adjustable sports that I had revalved and made into double adjustables by Koni NA. Used on my now gone 1989 C4 Corvette for SCCA Solo events, they won 3 national championships and a Pro Solo title since 2006. Should work fine on a BSP or road racing car, I believe these fit 89-96. 2.5 sweeps of rebound adjustment on top and 12 clicks of compression adjustment below. Shock dyno graphs included with purchase.

http://www.cashmo.org/VettePics/C4.koni.doubles.jpg

Price = $950 includes shipping to the lower 48 states. Email cashmo at hotmail dot com