Yeah, as I said, both the Classic and Classic II use the exact same slot, just that they're wired up differently, due to the differing purposes for which they're used, so they're physically compatible, but not electrically compatible. I personally wouldn't do it, for fear of damaging the card, the logic board, or both.

For the record, no, the Classic doesn't have any RAM slots on the mobo, but most of the RAM expansion cards typically have 2 - 4 slots from memory.