Owen_Dyneto wrote:
My strong personal preference is for the scissor-type valve spring compressor as typified by the K-D unit pictured below. I've used this one for dozens of L-head engine valve jobs, never a moment of dissatisfaction.

K-D also made a tool to insert the keepers, again pictured below. In this case I don't feel the tool is useful, I've found it much easier to put the keepers on by hand with just a dab of grease on the backside to hold them in place while the spring and retainer is lower.