I have used these lowering kits before and they are counter intuitive. At first blush the idea of adding springs to make the bike lower seems wrong, but its not.
You can do the install with the forks on the bike ( IMHO it's easier). The is a chart on progressives web site (and I recall on fast eddys as well) that shows you the correct spacer length for your bike. You likely will have to cut down some spacers to suit. The kits are somewhat universal.

05 speedmaster - 1100cc, 11:1 racing pistons, Carillo rods, thunderbike cams, ported and polished head, 2mm over intake and exhaust valves, Barnett kevlar clutch, scepter pipes, oversize manifolds, 45mm HSR's, TTP stage 4 firestarter