I don't now for sure but I'd expect you're right.
If you need any measurements I've got an '89 D250,'85 D350, and '76 W200.
I would caution you, there is almost no selection of 16.5 tires, and both 16.5 and 16 inch truck tires are all over $125 each, at least in my area.
If you know of any cheaper choices let me know!