If you ask me, I would stretch the WB at least up to 95", thinking on handling/stability and the lenght of the rear driveshaft.
The WB on my MB is exactly 89", with the same drivetrain, and my rear driveshaft is only 17" long.
I also like the "stock body" apereance, but adding 10" at the middle ("door openings") even looks better. Also is nice to have more space for the seat.
My 2 cents.