The retainer kit we are using (TFS-2500286P) has shorter valve seals than stock to clear the additional compression of the spring from the additional lobe lift of the cam.

This isn't difficult if you have the correct tools. Several companies offer an on-head spring compressor; we chose the TFS tool, but Comp Cams and Crane offer similar versions.

Proform's new Pneumatic Valve Spring Compressor can cut cylinder head disassembly time in half. Pulling the tool's trigger supplies up to 350 pounds of force using 125-psi air-compressor pressure ...