Russ, I've got a greddy M spec if you want to test it. I'll measure it tomorrow, but I think it should fit. Its on my car, but as usual my car never gets driven so you're welcome to pull bits off it.
It was a fairly cheap kit so probably isn't the greatest core, I have no idea how well it flows but you could test it. If it works we can sort something out, at least until superlap.
Let me know if you want to try it.