The deck height is out by a couple of mm I seem to remember. I looked into it a while ago, found it was not viable and promptly forgot the details [my brain operates on a need to know these days]
Pistons are still available up to 1mm oversize, DR, GN,SP they are all the same and the rings for the SP/DR 500 are identical and the same part number
I've got a few good old pistons, may well have a +1mm
If you haven't got a decent dealer in your country Crooks Suzuki in the UK are excellent and know what is available from Suzuki at a touch of a button.