I have a 1998 SX Cobra and was told that i could use any DP-SM lower on my upper to make my single prop a duo prop. Does this sound right?
Yes, you can replace the lower unit to convert to DP, but you can't use just "Any" lower unit. You need one with the proper gear ratio for your engine.
2007 was the first year of the DPS-A, and exactly why year of the boat is worthless as to what the year of the engine and drive is.
If the drive is a DP-SM, then it's not 2007, probably 2006 but yes it will fit your "98" drive. The 1.95 gear ratio is for a small block Chevy V8, what engine you actually have, I have no clue.
That is what you want.
It is not at 2007 DPS-A