G'day Mike

A really good way to look for a bike is asking a forum like this.
Basically you have the choice of the iron head Golden Flash or the sporty alloy head Super Rocket in the 650's or A7 iron head or Shooting Star in the 500's. 59 is a good year as most of the bugs had been sorted by then. As BS said
"They are not bad to work on, spares are plentiful and advice is easy to come by.", plus there are many up grades available eg electronic ignition, belt primaries etc etc.
Basically depends on how much you want to spend or how much work you want to do.
Cheers