[Mr.R]

I have to partially disagree with Bob here engine parts a quite easy to come by but as Bob has said they aren't cheap!
A new bigend/conrod assembly can cost as much as £500 for top quality kit.
Complete transmitions can be had from Nova Engineering and others.
You can buy almost every engine part new,(apart from the main castings) as most if not all parts are still being made today...
At a price!
Topend parts for the motor are the same as the Widecase models.
If you're going to put the bike on the road you really need to convert it to 12V electrics, if you want any chance of seeing where you're going after dark.
With a bike of this age I'd recommend a full re-wire, updating as many parts as you can.
There's available a complete alternator conversion that will power a modern electronic ignition system and a Halogen headlight along with the rest of the system.
You can also buy a conversion that will power the ignition without a battery, it's a CDI type which originally was meant for an off road/race Yamaha...
Both of these kits come from Australia which's a very good source for singles parts.
The DOC of Canada has some good info on their homepage about how to prepare and set up a single for racing.
If fully rebuilt the motors are quite reliable as long as you don't slog them, they need to be revved.
In this country Lacey Engineering, Brancato Engineering, MotoMariana and DTS (Ducati Technical Services) are good places to start but none of these guys are cheap!!!!
It's more than possible/likely to spend more on a single than would buy you a decent 996SPS.

Steve