I have bought a couple of these. They fit straight in the hole in the nacelle but do require some surgery on the speedo cable. I ended up getting an Enfield cable, taking the the end that screws into the speedo off the outer. I then did the same to the BSA cable and grafted the Enfield one on. The square part of the inner cable was lightly smaller on the Enfield speedo but I have an old, original, speedo cable end making press thing I bought off EBay which sorted the problem.
However one thing to note is these speedos are a little on the temperamental side. Both of mine have a habit of getting stuck at a speed and then appearing to "add" the current speed on to the "stuck" figure. I have seen 120mph on the A7!
Slackening the nut on the back of the cable where it enters the speedo does seem to help with this though. The strange thing is when the speedo stops reading correctly the odometer still works fine.
On the whole the speedo looks fine and sometimes reads the correct speed which is OK by me.
Z
