I've also got a C3 with PR40. Mighty good sound! The best is to have a PR40 AND a 122 cranking together....
However, you'll need to buy a whole C3 to 122 connector kit, it involves the half moon switches etc. I can do a search for you, but I don't have the details right now. The kits tend to be a bit pricey, but you can also get the details of whats involved, and you may be able to build something. I'll be back in a moment!