I know for a fact that Tein Flexes are the same part number for the GSX and GST.
In fact, I've ran the Tein's on my GSX but they were bought for my late GST.
IMHO, the flexes are way to rough on the road on a GST, but on a GSX, it is really an awesome ride.
In order to answer your questions better, we need to know what brand adjustable coilovers you have.
As far as everything mounting up, they are a direct fit.