The PBY-6A had a radome mounted above the cockpit just forward of the wing mount. Black Cat PBYs were also field-modified with MAD systems (Magnetic Anomaly Detectors) to locate enemy shipping in the darkness, and could also be used to track submarines running shallow.
PBYs WERE used for carrying supplies. The early Black Cats (or at least their forerunners) were extensively pressed into helping resupply Guadalcanal, although their carrying capacity was understandably limited. However they were NOT utilized as troop transports. The closest they came was air-sea rescue operations ("Dumbos") and occasionally as long-range VIP transports.
Sector9,
All PBYs ran armed, including those operating as scouts. Standard armament in the PBY-5A was 1 or 2 .30cal in the nose, a .30cal aft, and a .50cal in each waist blister. Most of the 5As had the twin .30s, so this is the package that should be modeled. The PBY-6A replaced the bow .30s with a pair of .50cal.
A large number of Black Cat PBYs added an additional four fixed .50cal in the bow where the glass panel would normally be, just below the turret and which didn't interfere with its operation. It was technically a field mod, but was standardized enough among the Black Cats to IMO justify its inclusion as a gun package option. The bomb sight was removed in this configuration, so it could be treated like the glass vs. solid-nosed B-25C. Some Black Cats were mounted with a pair of 20mm in this position instead, however this required removal of the guns in the bow turret. I don't have any numbers for aircraft with this armament, so I don't know if it could be justified as a gun package or not.