Poppy, Keep away from those forks, instead spend time researching until you know exactly what to buy and that the part offered is the correct one.
Draganfly have had a mention and I would endorse the use of their online catalogue, but would also add that sometimes even they can have their problems. The forum has a section for suppliers that Forum members have found to be very helpful, two of note are Priory Magnetos and Brightspark Magnetos, both run by fellas who are both enthusiasts and know their stuff.
The Longstroke Parts Catalogue along with later versions can be found in the Forum Literature Section. Later versions feature the more usual exploded diagrams, the Longstroke one is more of a parts list, but with useful and detailed line drawings of the actual parts. Roy Bacons book "BSA Twin Restoration" publisher in 1986 is one to look out for.
As always I would make haste slowly, bearing in mind all projects like this will swallow the cash as mistakes are made through inexperience with unfamiliar designs.
Longstroke engine plates look the same as normal plunger ones, but the crankcase profiles are just ever so slightly different, hence the differing holes.
For that frame you need a set of Plunger Yokes. These and the later Swing Arm type differ in the position of the turn stops on the lower yoke, and early versions of the top yoke do not have a hole for the steering lock. Fork stanchions, bushes, seals and oilseal holders are common across the range. Fork sliders all have the same bore, but differ depending on mudguard mountings, wheel hub type, torque arm arrangement, backplate stop and spindle type for starters. Headstock bearings are common across the range.
For now I'd say get it back home undercover and give it a big dose of looking at. A notebook is useful to keep track of what's where and what it all cost.
Swarfy..
Additional. Thanks to GB for more details of engine fitment. It's a lot easier with some help, it can be a good wriggle and a juggle to get all the parts in place at the same time.
