>>1728526>are there mods to go 650b and thicc?I mean, yeah, if you're down to move those calipers down the fork a bit, or potentially switch to disc brakes - you could get a fork with disc brake mounting lugs, but you'd still have to braze them onto the rear dropouts, too. Or drill more holes for the caliper brakes you've got already. Maybe there's a mounting adapter you could buy or perhaps you could diy one with some sheet metal if appropriate thickness, just to move the brakes to accommodate the smaller rim diameter.
If it's a fixed gear you could just drop the brakes and put whatever wheels would fit in there. Otherwise I'm not sure there's a solution that would be easily worthwhile.