Wouldn't these spindles have a ground finish?
It would depend on what you can get with the equipment you have as far as finish and size spec.
Grinding is expensive, and if you can avoid it you would.
If I was going to make this, I was going to make this I would use something like 8620 and tell heat treat I needed a excellent finish (which costs more, but way less than grinding) and see what we get during inspect.
If it sucks, than no choice but to grind and charge accordingly.