No idea on power gains since we did a bunch of stuff at once (TVS, intake, exhaust, etc) but the car drove around town very well and made good power all around. It continued to make power to 7k with these cams as well. I do have some idle videos, but they're on Facebook. If you can shoot me a PM I'll work on sending them to you.
I'm 99% sure we re used the retainers, so they wouldn't be available. Springs are recommended if you're going to race the car in any capacity, but if you just want your car to sound cool then you wouldn't need springs.