being an ex lardy owner and some what obsessed with the GS160, id ditch the original engine to be honest parts for it are impossible to get and its a unique engine that shares no parts with other vespa's.
Theres 2 GS 160 engines on ebay at the moment one at £1200 and the other at £800.
also being piston ported theyre 5% mix and slow too and unreliable so really not worth bothering.
id stick the engine on ebay as individual parts and put it towards a tidy px200 engine. all you need to fit it is the a special engine mounting bracket from SIP and upgrade to 12v wiring
rare it is for sure you go to spain and find one ,people who i know on facebook who live in spain dont see them anymore the early vespa ones .mine is been sprayed silver now i will put some pictures in your email for you cheers,
oh forgot something aswell ,,just keep a hold on to it for a month or two .when you see what ive done to my scooter ,they will all want one for sure ,but no chance of one ,so keep it and you will see something cool
I'll spare you all the pics of my failed attempts at fitting the crank and bearings and pretend it was a peice of cake ;D Which it actually was once I'd stopped dicking around. And the kickstart spring nearly went across the garage more than once the b`stard.
And the Haynes actually proved useful - couldnt work out why the cases wouldnt go together - had to fit the kickstart so I could move the quadrant.