Clutch line inner diameter

I finally got my howes racing clutch m/c. its gonna be a pain in the butt to adapt it to the existing line, so I think I'll make a custom braided steel one with russel components. now who knows what the inside dia. of the stock line is? I dont have one lying around and I dont want to take mine off till the parts arrive. russel offers brake line stuff in -3(1/8) or -4(3/16). most of the stuff I like in their catalogue is -3 but I suspect its gonna need -4. any expert advice here?
thanks,scott