Andy's right about fork height, I had mine (in an mc28) droppped about 15mm, but when I had the rear shock and forks tweaked by k-tech that 15mm drop resulted in a bike that was far too twitchy (presumably as the rear shock was now running a bit higher), they're through about 5mm now.

As regard tyres, Dunlop Alpha10's for the road without doubt, they're currently £110 a pair in 110 and 150 sizes at M&P!

But for outright grip? All the fast fast F250 boys run Michelin Supermoto tyres, they're treaded but not road legal. You could struggle to get them hot enough on the road as well.
Another problem is they're only available in 120 and 160 sizes so you really want a 3.5" front wheel, ideally a Magtek intended for an RS or RC30/45, but the front wheel from any old Honda 400/600 from the mid/late 90's will fit.
However you are compromising handling for a slight grip increase you'll never need and there is no doubt the 110 front on a 3" rim does result in a sweeter handling bike. I know of at least one very very quick guy who's run a 3" rim on a 400 with success.

But if you fancy oversized tyres/rims and are chasing outright grip consider the Maxxis Goldspeed road legal inters, I've used the StreetSport version (on stock sized NSR rims) which are the hardest version of them and they're really good especially if the road is less than bone dry.
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