The only reason I would run my main ground to the aluminum head is just to prove a point that it would work. Aluminum isn't as good a conductor and it has problems oxidizing in open air connections, so I wouldn't use the head for a ground permanently. Just to prove a point that no matter how much thread sealant you put on the bolts will not stop them from making a good electrical connection to the block! Whether it be teflon tape, pipe dope, or thread sealant, it simply will not electrically insulate a tight connection. And as in the previous post, it doesn't make a bit of difference if it's a square wave, a sine wave, or straight DC voltage.
I looked up alumilux and can't find it. What most electricians use on aluminum connections IS NOT conductive. It shields out the elements to stop the aluminum from oxidizing and causing a poor connection. They do make conductive greases, but they are not commonly found in a home wiring, such as where the aluminum mains come into the breaker box from the transformer. That's not conductive grease, none I've seen anyway. Not the grease the electrician used in my house or garage.
I get it, I really do get it. You like ground wires. That's OK in my book, they won't hurt a thing. Again, I was replying to the remark about thread sealant causing a poor electrical connection.