I put the larger front wheels/tires on my 310, and do not have any problems. Feel free to judge for yourself:

The nose is lifted maybe 1/2 inch, but this does not affect any decks, or implements I would use in any way.
I have never understood where the idea of using 8 inch wheels set tractors too high. The 400 series use the same front axles and spindles as a 300, so how does it make them higher?
The sole purpose of using the 6 inch rims on a 300 series was to allow clearance for the 37 inch SD decks. If you use one of those with 8 inch front wheels, you're gonna have issues- When you turn left (all the way to the stops), the left wheel will contact the deck. Use a 36 RD or anything up to a 48 SD, and you'll be fine. Just not the 37 SD...
Kevin