i just built a set for a wissota Midwest mod (similar to sport mod) a week ago.
they are performing noticeably better than his oem set, and the castings do indeed look nicer, but i wasn't impressed with the machine work compared to earlier ones.
i had a couple of exhaust guides that the valves (manley, not cheap junk) wouldn't even go into.
i expect to touch up valve jobs, maybe even touch up guide sizes a bit, but the fact that they were so far out that a valve wouldn't even go in is not confidence inspiring.
i like the heads, better than i though i would, so i hope this was just a little hiccup while they are trying to increase their production rates.