If you get a half cut you don't really know know the history of the engine and box, i mean it might hold together or might let go its really hard to say, but stock in a KE70 for driting and stripped interior and setup properly i would not envision you have issues,
It will be trial and error, don't quote me as I'm not up to speed in terms of drifting knowledge
My 30 was an auto in its previous guise, so is larger yes and did not need the tunnel massaged, depends how you sit the motor in, i envision should clear the tunnel, others have had to give it a tap here and there,
and yes the shifter does sit very close to the handbrake, you can shorten the handbrake itself or even buy a kit, mine is slightly angled yes, and when up i cannot get into reverse at the same time
http://www.my105.com/listingdetails.aspx?id=5481&latest=1