If it's bored and stroked to a total of 600(actually 612), then that's a normal bore/stroke kit that's available, and should be okay.
The bore should be around 87mm nominal.
If the bore was made bigger than that for whatever reason, it should be a simple matter to get a new jug and piston to put it back to 84-87mm(whichever you want).
There were a few 89 or 90mm jobs out there which used converted Harley pistons and a real oversized bore job which didn't turn out so well.
In general, if the bike has some issues with the piston and cylinder, and nothing else is butchered, it's not a big deal to get it back to right again. It would cost some money, but it could easily be done.