from rockauto, here's the specs for the sealed power replacement:

http://info.rockauto.com/SealedPower/VS1456.html

granted, typical installed height is ~1.62". I measured coil bind with a vice and a calipers at 1.1", so that is .52" of travel, or .480-.490" of safe lift capacity.

based on the info given, it calculates to a rate of around 240lb/in, and a seat pressure of ~94 [Email]lbs@1.615"[/Email] IH.

for an aggresive roller like the hughes, you need lots of seat pressure, something in the 120-150lb range, to keep the valve from bouncing when closing.

I'm running a reground LA roller cam in my hybrid roller LA/mag headed 318. Bullet Cams reground it for me, and I spec'd out their HR259/316 lobe for both the intake and exhaust. it's 259 adv, 208@.050, 127@.2 and .316" lobe lift, which calculates to .506 with 1.6 mag rockers. it's been an awesome combo for my heavy (3900lbs w/o driver) 5th ave. pulls as hard as my XE262 equipped 360 that was in there before, but averaging a respectable 17mpg in mixed driving.

with the mags, especially if you do a little clean up work to the bowls and ports, you don't need a split pattern cam. using the same lobe for both will reduce overlap and give you a smoother idle.