The thing with those single log style turbo kits, which is what i'm assuming you're building, i don't think you mentioned it; is that there are no left and right banks anymore. so, just put the driver's side o2 in it's stock location and the passenger side o2 in the downpipe about where the trans and engine bolt together.
shouldn't be any lengthening required.

however, if you're building a two into one style, like a ypipe, and your o2 connectors are square, send erica a pm with the length and we can make one for you