I would keep the LS transmission and install an aftermarket LSD. The LS gears are pretty tall - taller than the GSR and Type-R gear ratios I believe. All you need is the power to back it up and use the full gear length.
I think the B-series VTEC motor gear ratios are all shorter than non-VTEC. I might be wrong. My B16A gear ratios are pretty short though. 80mph on the highway usually puts me at about 5,000rpms in 5th gear.