There are a couple of things that you have to do and changing the motor base is not one. In fact this is the biggest PITA about these seats as you have tomanually turn the motor to move the seat to get to the mount screws.

The seat belt control bracket, seatbelt lock and sensor wire will need to be exchanged to the other seat.
If you have an arm rest then you can change the seatbacks also quite easily. But be careful threading the motor wires through the seat.

The plug-ins for the seat controls are both the same so this should not be an issue.
I can go into much more detail if you decide to do it.

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'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique