Yeah ill have to say the RB25 trans would of been much less work, and a lot lighter!
I can't say im much of a 2jz fan, but a swap is easier to accomplish on the toyota rather than the nissan rb26 on the sole fact of the turbo/exhaust arrangement is preferable for routing the steering column. Very familliar with the RB26dett however, and would go to great lengths to get one in there(electric power steering!)
Now on the SR20 motor, sure its cool to have the J-spec motor and all....
but the turbo KA will make WAAAAYYYYY more torque, be a hell of a lot more reliable on the top end, and most importantly can make full boost at all of 1500 to 2000 RPM. By the time the SR is making its way to full boost(6000 RPM) you, the smart crafty one in the turbo KA will be at full boost in third gear

A good friend of mine is making 260 horse and 470 torque on all of 8 Lbs of boost(granted its a built longblock< AEM brain box, MSD DIS-4, and coil over plug from a CBR 1000

)
Check it out the madness for yourself:
KA-T.org - The Home of 1000+ whp/7 sec Turbo KA's