The best I can do is 64ths of an inch, so:
41/64 wide, 5/8 + a 64th That's measured at the ends, all of my cars bow inward slightly in the middle, but if the sides are forced out straight, they;re the same width there.
2 63/64 long, 1/64 short of 3 inches.
That's at the top. If there's any taper, the bottom will be smaller, but I can't measure that with my ruler.