A cruiser? are those built well enough? thats what I'm riding now, (not old like you said) And there arent a lot of options for suspension.
If it's steel, it's built to last.
If it's newer than 1970s, it's probably not steel.
Don't do what so many do who buy some FEMA-Mart Chinaluminum job, slap an engine on it and go self-destruct within a few weeks.
Cruise local yard sales, thrift shops, flea markets - even dumpsters - bike stores, heck, even Craigslist.
That Garelli you have should be steel, it's not a bad platform for a motor - definitely beats all of those Cruiser-clones they sell now - but it would be kind of a shame to do that to a minor classic road bike.
I have a 1961 Schwinn Tornado - ladies' version - that I've been planning to turn into a 'Chopper' for a long time, just haven't gotten around to it.
'Inherited' it from the Ex, it's good Chicago steel - this is one HEAVY bike - which makes it a pain to pedal uphill, especially since you have only 1 gear, that's 1 reason why motor.
Reason no.2 is the shape, top tube as well as downtube follow the same downward curving path - to make room for flowing skirts.
When's the last time you've seen a girl in a skirt ride a bicycle ?
When's the last time you've seen a girl in anything ride a bicycle ?
Anyway, that shape makes it look a lot like a Mofa or some Lo-ridah Choopers, reason no.2 why I started thinking motor.
The Ex's brothers also swapped the original Townie handlebar for apehangers possibly taken from a Stingray, further enhancing the Chopper look.
Since the original fork made no allowances for any brakes and I don't like the idea or the hassle of disc brakes, I got a different fork, also had to change the stem because rust.
Look for something like that, men's model would be better.