Sounds about right to me, the only reference material I can lay my hands on atm is Mick Walkers Ducati 4 valve twins where theres scant mention of the SP (btw the use of SP1 is just to stop the issue getting clouded with people asking "but which SP ?"
) and Ian Falloons Ducati desmoquattro performance hand book .
Mick Walker briefly mentions it and says sod all except it was an 888 and Ian Falloon briefly mentions it but thats about it .
Thanks for the heads up on the chassis number , I now have no niggling doubts as to my bike (Not that I did ) but now know its what I always thought it was , A 1989 851 Monoposto with an 888 engine