I'll not hi-jack Stuart Bs thread.......

So, I'm after a duel circuit M/C for my Plastic car. It has no servo and standard Esc2 brakes (although soon to have Capri big rear ndrums). I'm thinking I need 0.7" bore. Does that sound right? And where do I get such things? What car do they come from? Part numbers?
Cheers, Owelly.