Hi Kevin, The two adjustable spacers you mention are there to hold the rear of the gearbox in position. The riders footrest spindle passes through them and when tightened up secures the rear of the gearbox in position. If you can't obtain any I suggest you place engine and gearbox in frame, tighten up the front mounts, and then measure the distance of gearbox to frame on each side (different lengths) and get a pair made up. The fact that they're not adjustable shouldn't make much difference as long as the frame is straight. Take note that the spring clip for the centre stand is held by the footrest spindle on the right, so allow a couple of mm for that.
Hope this helps. Dave.
