Just installed a 3rd row on my xc90

[gmbhgmbh]

I was a bit adraid to do this as I coudln't find any post anywhere of anyone that had done this, but it was a lot easier than expected.
Your xc90 is already built to accomodate that 3rd row including seatbelts but the real difference between the 5 seater and the 7 seater is actually the 2nd row. The 2nd row seats are different as they slide to allow for easier access to the 3rd row, so what you'll need is a 7 seater doner car because you'll need to replace the entire 2nd row seats, all the plastic trim pieces including the b pillars, c pillars and any trim in between, you'll need the seatbelts and you'll need to change out the boot parts.
It sounds a lot bigger job than what it really is but cost-wise, you'll be far better off buying everything all at once from a salvage yard. I bought it all for £550 and it made sense in my case since I couldn't find a good 7 seater so I opted for a good 5 seater and added that 3rd row.

I hope this helps anyone thinking of adding that 3rd row.