Bulgarian MBT today is T-72.We had more than 2000 T-54/55, some 260 T-62, but they are all gone now-either sold, or scrapped or in conservation.
I met my friend this evening and he told me, that Bulgaria did not have Volna version, but recieved from SU some T-55 AJ(Т-55АЖ) also known as T-55 AK or T-55 AM1.They had the russian KDT-1 laser range finder,rubber sideskirts,SODA napalm-protection, but lacked the turret protective reactive armour-the "chins" on both sides of the turret's front.
Such tank being loaded for sale to a African country in late 90's can be seen here:https://www.youtube.com/watch?v=j0V0auOEjwU