I just moved to San Diego, and we have a relaxed, low-stress, local
tracklocross series here. Seems very much a "rung what you brung," but my wife is OK with me building another bike for it, so I might as well brung something neat!
So far, I've been looking at 70s/80s road and MTB frames with horizontal(ish) dropouts. Lots of cool stuff there, some lugs, and some of the paintjobs are epic if they aren't shredded (huge fan of Peugeot paint jobs, with bonus points if they have non-French threading.
I was wondering, though--has anyone taken a legit track frame (something NJSish) and slapped on some 650b track wheels to get clearance for CX tires? That would LOOK super cool (and also give me a real track bike with a wheel swap), but I have no idea what a geo like that would do on even a gentle cross course. I mean, they weren't really designed for hills, or even turning, though plenty of hipster fixie folks ride them in streets.
Then again, I've never seen a real track bike in SSCX, and people ride all sorts of stuff, so there must be a reason?