[RoyJackson]

You'll probably have to have these made at a machine shop. You'll also need longer studs to mount the spaced out wheel rims.

I believe your manual suggests swapping the tires side to side to increase the track (distance between the wheels). Have you investigated this yet? I swapped my front wheels side to side to increase the track for loader operations and side slope stability. It did help...I gained 4-6" total increase (eyeball job, not measured).
Personally, I'm a believer in filling the rear tires to aid in stability. The liquid gets the weight as low as possible. This increases the resistance to the tractor to roll to the side.
I know this was the topic of a recent thread comparing fluid filled tires to wheel weights. I believe you were a poster in that thread, Nuru...

Anyway, I'd swap those rear tires around before adding spacers.