The GP32 is one of the older 908 parts, so I don't remember exactly what the change was, but more than likely it was a die change which didn't affect the MON08 circuitry.
If I were you, I would consider the 908AP32. It's a newer part with similar features and less expensive.
Or the 9S08GB32, better features + built in BDM.
uCTechnoGeek