On the Timetable World website (
http://www.timetableworld.com/book_viewer.php?id=9§ion_id=3) I found a German
1962 timetable showing international connections (click the link
E7 Basel-Italy and zoom in):
an 0850 Milano-Bologna-Firenze-Roma arrive 1500 "Rapido", 1st class only express, with a connection to Messina arrive 0005 and Palermo 0726...
and a 1300 Milano-Bologna-Firenze-Roma arrive 2000 express, with a connection to Messina arrive 0825 and Palermo 1335.
So you're looking at about 24 hours travelling from Milan to Sicily, depending on where in Sicily your destination is.
It appears that the National Railway Museum has a
1967 Thomas Cook international timetable, on
http://www.nrm.org.uk/ResearchAndArchive/archiveandlibrarycollections/Timetables.aspx and click the link
Bradshaw and other continental railway guides list for a PDF listing of what they have available.
My own
1963 Southern Region timetable shows the Paris Night Ferry service as follows:
train: Victoria dep 2100, Dover Marine arrive 2230 (restaurant for sleeping car passengers, buffet for non-sleeping car passengers, 1st-class only sleeping cars between London and Paris)
boat: depart Dover 2330 arrive Dunkerque 0320 (0420 European time)
train: Dunkerque dep 0500 Paris Nord arr 0840
i.e. the 2nd class passengers had to get off the train at Dover and get on another one at Dunkerque.
2nd class single London-Dunkerque-Paris £4-19-0 (4 pounds 19 shillings)
No other info in that timetable, other than an advert for "Continental Services" including the 0900 from Victoria via Dover for "Paris, Riviera, Switzerland, Italy etc.", which I'd very much like to hear as an announcement!
Yet more info for comparison: my own
1978 BR timetable "International" supplement shows a table F London and Paris to Firenze, Roma and Napoli, including a through train Paris to Napoli, depart 0817, arrive 1028 the next day, via Torino, Genova, Pisa, Roma.
Also a connection from London as follows 1100 Victoria, 1300 boat from Dover, 1640 from Boulogne with through coaches (seated and sleeping) from Boulogne to Roma (the ROME EXPRESS) arrive 1320 the next day, also via Paris Gare de Lyon, Torino, Genova, Pisa. Connection to Napoli arrive 1553.
Hope all that gives you an idea of what was possible in days gone by. There was a surprising number of through coaches from the "mainland" side of the English Channel to parts of Europe - Calais to Innsbruck anyone? Hoek van Holland to Warsaw/Moscow?