why should one do this?
The other way round, a 600ccm barell at the 500ccm engine, that is the way to do it
But it should fit.
The 600cm cylinder has a slightly bigger neck, so there is something to do.
You will have a bigger gap, but i don't think that this will matter anything.
Oh and take care about the head gasket.
There is a difference in the position of the small holes for the water flow.
Make shure that they are not closed by the heads surface.
You may have to make new bores.
At least changing a Saturnos barell to a Nordie one, this is a common problem and ends up in overheating the head.
Oh and you will have to live with the smaller Saturno water pump.