As it happens, we have a PB4Y-2 at Yanks Air Museum. My partner and I just finished putting together one of the turrets. We are about to start on the other one, but instead of assembly, we want to overhaul and restore it, and then restore the first one. Our main issue with these is that when the aircraft was converted to a fire bomber, it appears they simply cut the turrets out and let them drop to the ground. Yes, we have to repair them, but the real issue is they cut the structural parts that hold the turrets in place. So, we have to either find a set of them or engineer new ones that will be safe when the aircraft is airborne. Wouldn't want to be in the turret, hit turbulence, and have the turret or turrets depart the aircraft!
Yanks' PB4Y-2 is B2872G, Tanks 124, BuNo 66300. You can see it in the PATSU Page. Click the link and go all the way to the bottom under "Recycle AC." That particular aircraft was modified into a fire bomber and the engines are not stock. The stock nacelles have been replaced with four B-25 nacelles and the engines are now R-2600s.