[Zeke]

Your pics from different angles don't show the mount that well. Welding will produce a lot of heat so not so good unless you have a bare block or at least no gaskets in the area. Also requires a lengthy cool down which is difficult in that situation.

You might consider brazing (silicon bronze) but some conditions are still the same — a lot of concentrated heat. not as hot and no cool down, but still....

Mechanical fastening is possible with machining a part. I even think some 3D printing is now strong enough.

I wish I could see that better. Obviously torque is going to work on that in both directions, so just supporting it won't work. I've seen some good Rube Goldberg solutions on other objects so keep thinking.