I want this Lunati Cam, Duration @ .050 (Int/Exh): 213/219
(Int/Exh): .455/.468 LSA/ICL: 112/108
RPM Range: 1000-5300. The whole Kit and Kaboodle has valve springs in it with seat pressure 120 and open pressure 330. I read on Crane's website that open seat pressure over 280 was too much for press in Studs. Lunati guy said press in Studs should be fine. Will 320 open pressure be too much? Or can I run the same cam with a weaker spring?

I don't know if it's too much but it's kind of alot. It's only too much when they start to pull out and all your rocker arms start flying off. 300lbs is usually the bench mark. I, personally, run around 320@.520LIFT but then I don't put many miles on the car and I realise at that pressure my cam is living on borrowed time. That's why I have two more sitting on the shelf just in case.

It's a crap shoot, especially with old heads, but you'll probably be OK.

I wouldn't.

Find yourself a set of heads with screw in studs. What CI engine?

I agree with Banshee. I guess I forgot to mention that mine are threaded studs and that I would not do what you are considering. I've heard many stories about noisy lifters in cars with pressed in studs and guys could never get them to quiet down because the studs pulled out.