Makakio,
You are correct. The SL320 does come with the 104 engine. I noticed that the pre-owned SL price has come down somewhat and I think it has a lot to do with the upcoming change of body style. I am pretty sure you can find a low mileage, late model SL320 for less than $50K. I have seen quite a few sitting at the dealership recently.

95 R129
98 ML320