HHR valve spring recommendation

I am getting a Lunati hydraulic roller with 250/255 .630/.630 lift ground at 112
My 540 will have dart heads, 310 cc, with 2.25 intake/1.90 exhaust valves. Lifters will be crane long body. On lunati's website, they show a single spring with damper, this doesn't seem right. I wanted to run a dual w/damper with around 150-160 closed, 425-450 open and titanium retainers. Comments, opinions or recommendations?
Thanks :rolleyes:

I just received my cam yesterday. I am really disappointed, looks like a cast core, sending it back. Now I am thinking just going solid roller (voodoo) like my original plan. Does anyone know how reliable solid rollers are on a street car?
Thanks Ed