Seeing that by the time the Allies started helping Tito in Yugoslavia, the Beaufort was restricted to western Europe, so I would assume the wreckage is from a Beaufighter. You could research which RAF squadrons flew over that area, Allied airbases were on Italy's east coast & on the island of Korcula. Individual squadron histories may enable you to identify the actual plane & crew involved.
I am 99% sure the Beaufighter spar cap has a different part number to the Beaufort one. The end fittings definitely have the same part numbers on both types and the complete spar itself has a totally different part number naturally to reflect all the changes involved in carrying the extra guns and extra fuel tanks but unfortunately I do not have a tech drawing of the cap or a parts list of that area. The extra fuel tanks were a unit option and fitted in the gun bays instead of the guns. I do not know if that was universal but they were an option fitted to the IC and later aircraft.
The fighter also has much larger oil coolers and the mounts are on the front spar. The Beaufort oil cooler mount is parallel but I have never seen a fighter oil cooler mount so cannot say if it tapers. I would consider that highly unlikely.
I would be very surprised if they have the same number as the changes to the spar only need one hole in the cap to be different and then a new number is automatically required.
The same applies with the tail rib.
Hopefully Jan can find some more items with part numbers on them. Any fuselage or powerplant part would clinch the matter. Even engine, fin and most tailplane parts.
The main fuel tank parts will not be an indicator as the Beauforts originally had plain metal tanks which were replaced with Beaufighter self sealing tanks fairly early on.