Like the others said, the .380 Round Ball is best for most .36 caliber C&B revolvers although like mykeal said they are very hard to find, the .375 will most likely work but you will have to see if there is any lead ring after loading.
Most .44 caliber C&B revolvers work fine with a .454 Round Ball although my 15 year old Pietta 58' Remington likes the .457 Round Balls better "accuracy is better with them compared to a .454 ball" & my old Stone Mountain 51' Navy can almost thumb press the .454's into it's chambers so mileage will vary with gun to gun.