Norton Dominator 77 barrels

Hello everybody. I am restoring my Dominator 77, build in 1957 and as I know it has the same 600cc engine as the Dominator 99.
My problem now is that I will have to replace the barrels and pistons and I don't know the difference between the 500cc and the 600cc barrels.
For example I can see now on ebay a Dominator barrel, but the seller doesn't knows which model it is.
I was trying to attach some pictures with my barrels, but I can't see how.
Thanks in advance for your help.
Cheers

Not sure the size of the bores but if you know the size off your 600 bores then you will know which one it is as 500 bores be smaller size, if you have a manual would give the size bores for each model, I have to find my Dommie book and see, but not sure it be in my book as my Dommie is a 1960 650 Manxman, my Commando/Featherbed frame is a 57 Wideline but I bought the frame - the motor and GB.