I'm very jealous that you found a p6! I'm always looking towards Italy but everything is so expensive over there!
I'm pretty sure treatland do different front sprocket sizes for them, if you search for minarelli it should come up with some.
Strangely I was hoping to build a Kreidler style bike with a tomos at50 that a bloke gave me for nothing. I thought it was a 2 speed tomos but it turns out to be a 5 speed. There's a few bikes for me to build first.
What did you search for on eBay out of interest?
I enjoyed the long message, it's nice to find someone else trying to build racers.