I cannot suggest a facility as you indicate Italy as your location and I am in North America but you did request input. If you have experience having JT8's "Repaired" then this post may aid someone else.
I said "Repaired" because that is what is accomplished, not "Overhaul".
Spend some time and money and do an "Audit" on your choosen repair facility to check out their capabilities. Search and list what actually has to be done on the engine as far as AD's etc. Only do what is required and if parts are required then buy new as a last resort. There are engines disassembled all the time with lots of hours and calender time still on the parts. If you are not fully familiar with the engine strip down then hire someone who is and send them with the engine to monitor it from strip down to final test run. Saving 150 to 200 thousand US dollars per engine build is criticle. You also end up with an engine you have complete confidence in and hopefully no surprises when you hang it on.
Hope this helps someone. (Just my 2 cents worth)