certainly the 3 s13 boxes and two s14 boxes (when fitted with CA bellhousings) i have had, are all the same length, so you will need to shrten the prop anyway to fit s13 or S13/14 hybrid.
i have considered the OS Giken stuff, but my gerabox failures (to date
) have been selectors rather than gear sets. In my opinion, i could run 20-30% MORE horsepower than a 200SX and not break the gear sets or tailshafts due to the lower weight of the car. Its torque that kills the gear sets and bearings and im not dragging a 1200kg tin car about, but 750kg of plastic pig instead! so the loads are less, and the box is subjected to those loads for less time due to the quicker acceleration of a much lighter car. Trouble is by the time you have a Giken box built up, its nigh on 2 grand and it uses stock selectors and H pattern.
I toyed with a Quaife sequential box for a while, but i just couldnt justify £6k for a box, even if i could afford it. The more i looked into it, it wouldnt fit anyway as theres a dirty great lump on the drivers side of the box that just wouldnt go into the chassis (see Brens pics of his S14 monster build). The HKS sequential box that i saw at the Autosport show would fit however as its all in a std size casing
If i do buy a race box, and it wont be in the next 18months as it would probably require a class change, i would probably go for the HKS or more likely the PPG dog box with possibly an Ikeya shifter.