The hole isn’t deep enough to run a set screw in, and get a bolt to proper depth also. Factory studs WILL work with headers, if you use the thick factory cup washer that was in that spot with the manifolds. I’ve done that with many cheap headers back in the day. I think I discovered how to make that work right after I pulled the end studs out to put headers on my 70 Duster in high school. At least it ain’t like a big block, where they All go into water!
