If it's a 3 cyl, the exhaust / water jacket covers are carryover to the modern Clamshells, and shared with the 60 / 650. Later models (like the one I replaced mine from!) have painted water passages to reduce the corrosion and also are missing a small vent hole form the poppet valve cavity (Valve appears to have been deleted in later models).
Spark plug leads should be about £7 from your local friendly auto factor (or £25 form halfords
) Rubber bushes are also carryover to the newer machines, so if the lucky buyer knows of a siezed clamshell lurking somewhere, nice & cheap repairs. Just be aware that the top mount bushes will require a powerhead removal to change.
I should add I only make these comments as someone who has just rebuilt a variation of one of these, and I have no link whatsoever to tumbleweed.