The so-called frontline bikes were limited in the main to BSA, Matchless, Ariel and Norton, and all used in N Africa. Dont forget that the Matchless G3WO preceding the G3L has girder forks and its a nice (comparatively) lively ride, with OHV engine, though rarer (and more expensive)....as is the Norton. Latter is a pretty antequated design cf the Matchless and BSA and parts are more difficult/expensive to source. The Ariel is also a decent lively riding bike, also with OHV engine (and girders). They are all simple bikes made to be worked on with none a lemon. The Matchless is a bit more fiddly to work with but hardly taxing. As you are not that fussed about which frontline bike you want, probably the best course of action is just to find one of those in good, complete condition at mot silly money. And when you do, ask back here re the specific bike before you buy, as it might just save you much heartache and hassle! Motorcycles purporting to be complete and original frequently are offered at top dollar. They can look very nice.......and be very wrong! The cost of putting such dogs right can be eye watering.