okay, i have a question, i know the panthers don't look like they're gonna have much of a team, and you probably feel a little embarrassed, but which offensive linemen are you? come on, 6'4, 310?? you have to play for the panthers. if not, show up, i'm sure they need the help.
moto-cross experience goes further than people give it credit for. especially when combined with an msf course to help break you of your bad-for-the-street habits.
i knew a guy who was 6'1-2, he weighed about 270. he insisted that he needed to start on a big bike. he bought a 900 ninja (monster in its day), and crashed it 4 times. after the third, i told him to sit on my f2 (i wasn't letting him ride it, he crashed 4 times in a year of riding). anyway, he was amazed at how comfortable and roomy it was. i would have to say the 91-4 cbr600f2 (94 being best) would be a good choice given your size and experience. ride it a year or two, then get a 'busa or a zx12r. if you don't like it, the f3 is a good second choice. you may want to look into the zx6e. it may be a bit low for ya, but if you like the katana 750, 6e should work fine.
the katana 750 isn't a bad choice, but here's why the 600 is better. 750-exclusive parts are usually harder to get. they are built on pretty much the same chassis. the 750 isn't that much stronger. the 600 is cheaper and easier to sell used.