245/75, or 225/75? I know all the Ford Econoline duallies used the latter.

 

245/75. thats what my doorjamb sticker says too.

 

The best mileage I ever got out of a set of tires were the factory BFG TA's that came on the '06

I got 120,000 km out of them, not super great in th mud or snow but I thought they were quite respectable.

On top of that I run probably 20%+ of my miles on gravel and tow with it regularily grossing up to 30,000#

I only ever rotated the BFG's ONCE and still got 120k

I replaced them with a set of Pirelli Scorpion take offs that are just terrible, a strictly highway tread pattern (which the tire gurus said would lead to better mileage out of them) they have no grip in the snow, mud or grass and at 50,000 kms are just about shot.

I'm thinking of going back to BFG's