It's nice out now, so I got one of mine out today to measure it.
Length between couplers: 73cm.
Width: 10.5
Height above rail top: 15.5
Unmodified cars ride very high, and too far apart.
Couplers can easily be remounted further back.
Lowering the car is a bit more interesting.
One way is to slide the floor out, and slide it back in one groove higher.