I watched TTT with George Bryce, he mentioned the Monster head has kz900/1000 stock type valves except 4 in each cylinder. He mentioned they were bulletproof back in the day when they didn't have rev limiters. The cams have kz lobes but twice as many.
It makes sense to not invent everything in the head, they might have KZ similar guides and adjusters also. I'm sure spring and retainer tech has changed a lot. He also said the original idea was a busa style head made for the GS block.
George also mentioned the riff between Steve J and Angelle. All in good fun, (maybe) Steve mentioned she can't work on the bike but spends pit time putting glitter on her leathers. She corrected that it's rhinestones, not glitter.