How much of a horsepower difference between these cams?
 

XE 230/236 .544/.555 112

XE 230/236 .578/.595 112

Basically the first cam is with 1.6 rockers and the second one is with 1.7 rockers.

I'm building a 383 with stage II heads that flow 260cfm@.550 lift and 268cfm at .600 lift.

How much of a hp difference will there be between the two rockers?

10-12 horse...tops. IMO, you need better heads. Not saying that your engine won't run well and make good torque, but horsepower won't be optimum without better heads. I would shoot for a good 20-30 cfm more of intake flow. How does the exhaust numbers look?

I don't remember the exhaust numbers but I know this guy's flowbench reads a bit low. There are guys with heads that flow the same as mine that run 11s on the identical cam in Vancouver at sea level.

Is that 10rwhp or flywheel?

It all depends. If your heads are still flowing good at the higer lift, then go with those. If they get turbulant or flow stalls harcore then go with the smaller lift.

FWIW, when I change lift on desktop dyno and the rate a where heads flow...at best it only seems to make for a few hp under most circumstances. There are exceptions to everything though.

its not worth 10 hp (if you get that depending on your heads) to chance thowing your valve train geometry off.

That's why you check for correct pushrod length...