11:1 and type b cam would equal a lumpy and snarling sounding car
by the looks of things, if you think that you will have enough low end with the 30, then go with type b
but if you do the mods like eug said, then i think you will be having to sacrifice some of the driveability, power etc with the 25 for a while (nothing lost, nothing gained they say...have to make sacrifices somewhere )
in regards to overlap, the r33 GTS and GTS-T cams are exactly the same, all thats different is the cam gears at the front - the turbo gears (i think!!) have a little more exhaust advance and more overlap, and the n/a gears have less overlap