Good advice thanks, I actually gave the cam and spring specs to the machine shop that did my heads so they purchased and installed the correct springs for the application. Not sure the exact part number of the springs but they are dual with a damper.
Regarding the noise it's actually surprisingly quiet. I read on Hughes Engines site that factory Magnum hydraulic roller lifters like .080-.095" of preload (quite a bit more than HFT's), they'll run fine with less but they'll be noisy. So I spec'd my pushrods for about .090" preload and there's basically no valvetrain noise. Certainly less than my previous 360 that had a small Lunati Voodoo HFT cam.
It does make excellent power, I really need some 3.55s in place of my current 2.94 gears because this thing pulls hard to 6000+ RPM and with my current trans/rear gears I can hit almost 70 MPH in first gear lol. No valve float or other weird stuff at the higher revs too, though again I don't get many chances to really rev it up because of the tall gearing. It has enough low-end and mid-range torque I usually shift around 4500 RPM when I'm getting on it around town and that's enough to pass anything. Normal driving it rarely goes over 2500 RPM and smooths out as soon as it gets above idle. Really quite impressive IMO considering the low air density and modest (9:1) compression. Racer Brown FTW!
Here's a video I took yesterday of it running to get an idea of the sound:
