why do you say that? the type r crank is an 87.2 mm stroke, the ls has an 89mm stroke. So between the two, you have to ask yourself, do i want better top end horse power or low end torque. since this isnt your engine, you cant make that determination. and since you didnt give a reason for your answer you took the power out of the builder's hands.
Also, if hes building for a turbo application youll want as much stroke as possible. High revs + turbo = bad. It can be done dont get me wrong, but the higher the revs go the more likely it is youre going to break something.
I (and most of the experienced members on this forum) am going to need more information on what youre plans are for this engine.