Found my dads original 1971 duster!

It's a shame the engine build wasn't a straight forward success but it is a success at this point. You have to understand this forum and all forums in general. When a problem is spotted, no mater how it turns out, some members will jump on it like a bulldog on a ham bone. Im sure the engine will be trouble free for a few reasons. The builder hid nothing and put it all in writing. He gave the defective head back to you for examination. He has a reputation as a premier engine shop to protect.
Don't worry about the engine, it will be great. One thing you might ask them is could they send a technician to oversee the initial start up. They may do that to ease your mind and also further their reputation.
Good luck and go have some fun.
Jerry