Donor Engine

[soulsurfer]

I'm exploring options for a Lambretta auto conversion and have someone in mind to do the work. I'm told I should look for a 2T air cooled Typhoon big drum rolling nut or SR125 or Skipper motor and that I'll need scissor arms, bolts.
This is all new to me so have a few questions...
I understand some of these are 4 stroke, but how do I tell, is it by year?
What is a rolling nut?
What should I look for, complete bike and sell on what I don't need, buy an unknown motor on it's own, standard or tuned, with or without wheels etc. etc. What sort of prices should I expect to pay?

Any guidance would be appreciated

Thanks

[hungdog]

Try here for answers https://www.facebook.com/groups/183275745114620/