I just went out with flashlight in hand to look..

Three of the tires (both front and rear drivers side) say 6.00 - 16

The rear passenger side says 6.70 and what could be a 15 or a 16.

I took a look again at that thread.. the 215 85R 16's sound like the way to go.

I'm assuming those are regular radial tires.. so they will go on the stock rims? Do you still need the tube?

an idea is only stupid if you think about it rationally.