All of Whelen's "can" shapes domes are interchangible size wise. Some used 2 screw mounting, some used dome clamp ring. The ring will work on the domes with screw holes..
I'm looking for a LED pole to put on my new bike, I'm friends with Whelen rep and no longer available, I'm trying overseas where they are still popular. If the new beacons would fit I might be interested in your pole if you decide to sell.