BAR bought all but 1 gun of RUAG stock, I would call them first to see what they have...
The 470 as you mentioned Barry will be the one to get, the longer under lever will make life much easier.
shootingmad, I used a lightened Diana 52 piston in my 440TH, it shortens the stroke....it needs to be lightened and while this is being done it would be rude to not add bearings
I have no idea what stroke is in the 470 however or if you are getting a sub12 UK version....