Some Zullo factoids:
I sent some questions in email to the info link at Zullo and got mail back from Tiziano himself.
The biggest production for Lewis Imports was late '83 - Spring '84.
There were 10 people working in the factory at that time, and were producing ~4000 units per year.
Some bikes built for Lewis may have been shipped without decals (and possibly without serial numbers).
Only frames were shipped to Lewis - no complete bikes.

Most of Zullo's work is TIG now, but he really enjoys brazing.
Workshop videos online:
Tiziano confirmed that it's him doing the brazing in the videos.