Yes, that would be a really helpful resource but currently I don't believe it exists. You're going to have to do some leg work and compare some geometries. That said, don't get too hung up on finding exact match to a SJ. I'd prob just suggest going with a 256 and doing the research to build it as it would suit your needs. Things like the amount of travel on the fork, rise and width of the handlebars, stem length and angle, etc can all factor in to how the bike rides. So you may find an exact match of a stumpy but you outfit it with different components of the one you rode and it would ride like a completely different bike. I honestly say just start with the 256 frame. My 2 cents.
That said, most of these chiner frames do have name brand counterparts that offer similar rides and geometry, I'm sure someone will chime in with what the 057 and 256 are close to, as I can't recall currently.
