Yeah, that's the barrel, 158, hhmmm. The bottom link with photo's from eskimo36
Too bad he had to have it on a new model frame. It wasn't a snap on though, I did pull the forearm off to double check it was indeed an sb2, and used the stubby philips screw driver I bring with for that purpose.
I didn't even bother to look at the lug for modification, as I was more interested in the frame.
I now have more knowledge, Thank You.