Just to add to this thread....I've recently had problems with a sticky thermostat, causing the temp to go close to the red. Having no success sourcing a thermostat locally or off the internet, the ones that were supplied were generic Fiat/Lancia with the by-pass outlet being 35mm rather than 25mm. Think we're subject to the "one size fits all" from motor factors trying to supply old Fiat/Lancia models.
I decided to fit a 75deg "in head stat" and adjust the pipework accordingly. The only problem I have noticed after fitting is, the temp sensors for the L-Jetronic are now on the cold side of the thermostat during the heat up period, meaning the fuel trimming for warm up is out of whack...but is barely noticeable and after three miles is back to normal operation.