This model was heavily inspired by the 2014 original eight-studs wide Ghostbusters Ecto-1 (set 21108) and a MOD of that set I found on Rebrickable. Instead of a late-50's Cadillac Miller-Meteor ambulance, it's now based on the (very similar) '59 Cadillac Eldorado.
In the changeover, I added a hardtop (removable) roof, different mirrors, 1/2-stud offset side-by-side seating for two, and opening doors. I also changed around the wheels to be less stressful to assemble compared to the original 2014 set.
Rear view, with driver's side door opened up. The opening doors were taken from the Ecto-1 and 2 (set 75828) from 2016.
The roof is only connected by two studs, making it easily removable. The car seats two figures easily.
I plan on getting one of these in real life in a different color sometime in the near future, probably soon after Emmet's house parts arrive from Bricklink.
Got any thoughts comments, or questions? Leave 'em below!