The Blue Magic head was what was written down on Lews notes that came with the engine. For all I know it may be just what Lew called it. It has a pronounced hemi combustion chamber and an angled plug like the Fox .15X
It was marketed as the Blue Magic head for a long time back in the early 90's when Tom Muggleton came up with the idea (and had at least 3 different versions). I vaguely recall that the Blue Magic was either a Muggleton Stage 3 or a close copy, but that could be wrong. Eric Rule would know/remember for sure.
The only performance improvement you can make by reasonable mechanical modifications/tweaks is by *increasing* the compression, which suggests the different heads. The improvement will be to permit it to hold a 4-stroke to higher RPM, and increase the effect of the break, which with the stock engine is *extremely gentle* no matter what it sounds like. It's the opposite of a conventional stunt engine, where if you hear something, it really changes a lot. This, the change is largely about the exhaust note changing - the difference between a 4 stroke and a 20stroke is negligible.
You can blueprint it much like Larry Foster did, but all that does is ensure that it runs properly stock. Almost everything done to it was to improve reliability/durability, not to improve the performance.
The easiest performance enhancement is still added nitro, that solves several issues at once, although not the most important one, the burp. Fortunately, we know how to fix that now and it's dirt cheap, easy, and there's no reason not to fix it.
Brett