Hmm.. that's wierd. At 73mph (confirmed on GPS) in 5th gear my GSR is at 4k, but my speedo says 80 or so.
I think a GSR or even a B16 tranny would be great for that motor. The only time an LS tranny is really used is when you have 500+ whp and you need the longer gearing so you're not blowing them off at 40mph and up.