what gasket cement to use?

No pics, sorry, I have no camera. But if you can figure out what you did there, then drilling the driveshaft is nothing lol.

I had thought of doing what you did, but didn't think it would survive long, so instead I just welded up a couple of cams, one each of 20*, and 22*, and I had a few factory ones besides.
Swapping cams only takes a few minutes with the screw up the middle, and I only did it a couple of times, cuz I figured one of the two would be right.

Best of luck with that.