Need tires for the farm truck

[Amphibious]

I originally posted this in the dually section in hopes that someone could help me. Hopefully i'll have better luck here.

Anyway, It's time (overdue) for new tires on the truck in my sig line. The rears are almost slick and the passenger-front is not in much better shape.
I am going to be doing a brake job at the same time, so the front wheels will be the correct dually style wheels, not the ones that are on it in the pic below.

The OE tire size is 235/85-16. That's what is on it now. I want a tire at least as large as these.

I've read/heard that the widest tire I can run without a spacer on the duals is a 265. True? I haven't been able to find a tire with a width of 235 to 265 thats any taller than what I have now.
I don't do much, if any, heavy hauling. Having the duals is way overkill for what I do with the truck.
I don't have a problem running spacers if they're necessary for the tires to fit right.

How much lift, if any, would I need to run a 285/75-16? I guess I'd need a spacer in between the duals. What size spacer would I need?
Whats the widest tire I can put on the OE steel wheels?
What about 305/70-16? or 315/75-16?

Whats the tallest/widest I could run with just a leveling lift and spacers in the back?

The big winch and bumper on the front have got to be making the front end sag after 13-14 years, too. Would I be better off getting new springs on the front to pick it up?

I'm open to suggestions. School me please!
I can post some pictures of the truck if it'll help.

Thanks,
Adam