I'm the furthest thing from a G1 collector, but more add ons like this would sway me. It looks damned good, and great review LMJ.
From what i've been told he does keep a small number of them. I'm hoping in july I will be reviewing a few more of his cassette addons if i can get the cassettes to go with.
I have one of the heads. Never used it. The only way to get it was to buy a rather pricy kit that included piledrivers for Frenzy and Rumble. I remember it was limited to a run of 100 pieces, but I can't remember what it cost off the top of my head ($50, maybe). I do know it was worth the price. These are great custom parts. As for just the head, I'd let it go for $25 shipped if anyone wants it.
I could have purchased one separately back then, I think I still have the email from the MJ guy somewhere. He was selling it on Ebay too for a while.
just PM MJ- I PM'ed him a while ago and asked and he said he is still casting these- I think he said $45 shipped for the soundwave head and roughly the same for the piledrivers if I remember correctly.