Keisler used to make a hydraulic actuator kit, but it's absent from their price list although 'listed' on their site. When it first came out it needed a restriction in the hydraulic circuit during high-speed shifts. Then this was "put in" their updated part,, and then it 'poof' disappeared.
I think if you have a nice firm mount, poly bushing on the rear engine support,(tranny mount). Nice diaphragm clutch like the Street Twin McCleod setup, the Z-Bar has the correct bushings in it, the transmission shift rods arent bent, the bushings in them are fresh and tight, the Bellhousing is true and faced properly, it doesnt get any better than this! I also went as far as using their bellhousing. I love my 4-Speed!