In my opinion you do not need to upgrade the stock valve train to run HKS 280's. I ran them for several thousand miles with the stock springs and retainers without any issues. With more aggressive cams (ramp profiles), i.e. Kelford 272's, or GSC S2s I would recommend upgrading the stock springs.

I'm not sure about the VIII Turbo, but I ran HKS 280's with a IX Turbo, and they were a substantial improvement over the stock cams.

Here are some good threads on the topic:

https://www.evolutionm.net/forums/ev...2-answers.html

https://www.evolutionm.net/forums/ev...2-answers.html

Dan (drb)