hey, a while back i was looking into this same thing. Your best bet is to just get a 650c or preferable a 26" with a 1 inch or 1.5 inch urban tire. A 26" with one of those specialized 1" tires is actually smaller than a 650c with a 23c tire. So i would do that, plus it will be waaaay stronger than a 650c, and youll have better/cheaper tire options.
But, i would still talk to gene over at spicer, he'll make you a fork for around 120$ (a lil more than a surly) and he might be able to accomadate your rake request. Also some other things that help with clearance, are 165mm cranks.
Something about the surly that you might not think of at first glance is that it accepts 38mm tires which means that the fork is longer, and thus is able to give you more clearance even though its only 38mm rake.
bottom line, dont mess around with 700c's if you wanna b-spin, cus even if you can find that one tiny spot that lets it go around it wont give you enough clearance to do anything that is actually worth the effort.