Have been looking at the same question for our 3400. I posted a question about this a month ago:
There were several replies, including a good pic from Ultradog of some fat alberts that were on one of his tractors.
Since then, I've been looking at this some more. Because of our loader(you didn't say if you have one), I'd like to get some wider front tires, wider than the worn 7.50x16's that we're running, like you. I'd also like to keep about the same diameter. Might be willing to get new front rims to get wider tires. Am also willing to run used truck tires like the 7.50's.
That led me to wonder what's out there besides 7.50x16's or the stocker tri-ribs. The other choices that I found:
235/85R16 - rims would have to be reversed
265/85R16 - new wider rims needed
11L-16 - new wider rims needed, might overload the spindles
This is distilled down from several tire and rim charts and I can't say that I know for certain that any of these would work ok. Also, not just any new rims might work, only those with specific offsets.