Googled up a few things but only this below item for sure from the same group.
Note it has Jumbo Racing, not Jumbo's also the ad refers to F1?
http://www.delcampe.net/page/item/id,202...language,E.html
Try and you may get lucky asking someone @ Shaver Racing in Torrance CA?
http://www.shaverengines.org/index.html
[img]<<GRAEMLIN_URL>>/dunno.gif[/img]
~ Pete