I picked up a Fulton A-1 upper a little which ago - haven't shot it yet, however a few observations.

Yes, it has a "delta ring".

Above the ejection port, there's a raised "A-3" marking - I'll take a pic of it sometime soon.

Yes, the front sight is set screwed - I believe its a practice for precision shooters, where they can mechanically center the sights. It appears that the screws are larger than taper pin diameter, so you'll probably need a new front sight post if you want to drill and pin it.

Like I said, I haven't shot it yet - but that being said, next time around, I'd probably just build one.

rd