Are they all blind holes or through?

Though.

I was hoping to chase one of the threads so it looks like that is out the question now.

Two things you may or may not want to hear. Fill the flutes of the tap with wheel bearing grease, this will hold the cuttings which probably won't amount to much anyway. Secondly what ever is not caught in the grease is aluminum so it really isn't going to hurt anything. That's what filters are for.

YMMV however so do whatever you are comfortable with.

I just repaired an intake hole in a 906 head a few weeks ago. Dampened paper shop towels stuffed under and around the hole, a wet/dry shop vac, brake clean, and a little bit of grease on the tap and it's a non-issue. No reason to pull the head.

I like what I am reading so far. I just cringe at the thought of potentially pulling the head. The grease trick has worked in the past using a back tap to repair a spark plug thread. Thank you guys.

try a "chaser" tap or a "roll form" tap. both with grease. very, very minute chips [if any] made. way better than using a "cut" [ordinary] tap if just cleaning up the threads is the goal.

I would second the suggestion to use a form tap, also called a roll tap. That style of tap literally forms threads in malleable materials (most steel, aluminum, brass, copper, etc.) without cutting, they are similar to a screw that extrudes the metal and forms threads. For your application get one that doesn't have flutes and you will have no chips if you lubricate it well.

Besides the obvious advantage of not producing chips it will force the metal back into shape instead of removing it and making the threads weaker and looser. That may not be a big issue unless the threads are really messed up, but it's still the best solution.

I agree on going that route, thanks for the tips.