I will STRONGLY advise you to have the crank and related bits DYNAMICALLY balanced, While I have yet to complete a A10 motor, I can say on many A65s they suffer from rocking couple and significant imbalances just as many other vertical twins do.
Nortons are the worst for this, and unthinkable in my mind to rebuild a Norton twin without a Dynamic balance. Triumphs have been 50/50 and gotten away with it many times, mostly with cheap shop customers who did not want to spend the dosh $$$$$$$$, But Rocking couple is inherent in the design and every A10 I ever saw vibrated quite a bit.
I can promise you 100% you will be very happy you did, I have NEVER built an engine for someone with Dynamic balancing who were not 100% highly impressed on how smooth it was when done.
If you dont ride it or just a static display, then thats a different matter. Just my opinion.
To do it properly you will need to discuss 1st with the shop doing it, But some are better than others. But the crank, sludge tube, plugs, rods, pistons, rings, pins & clips all need to go. Some balance their clutch baskets, timing gears and other rotating bits but thats highly optional, But on alternator model twins you SHOULD have the alternator rotor balanced as well. That is a HUGE lump flopping about and extrapolate the leverage of the lump its a no-brainer. Always interesting how far out some are, and how good others are as well but until checked you dont know. My guy does the rotors for $10.
Im sending out several Norton cranks soon for a couple builds and if you get over to the US I will be at the Norton INOA rally and you can try my N15 or Atlas. People consider them bone shakers and I can promise they will give you a new perspective on how smooth a balanced and blueprinted engine can be.