I guess mainly I think along the lines of minimizing parts you have to buy and then replace. The main improvements of the ITR head are a slight port/polish job, the cams, the manifold, and slightly larger throttle.

Instead of buying all that stuff, you can have a better port/polish job done on the GSR head, install the JUN or Toda cams, get a throttle which is even larger than the ITR one, and replace the intake manifold.

The only negative I see to that approach is if you can't handle the down time of taking off the head and sending it off to be ported and polished. In that case you could get pretty much any spare VTEC head and have that stuff done to it. Basically in stock form the ITR head is an incremental improvement over the GSR head but if you're fully building up the motor, anything that makes the ITR head is most likely going to be superceded. There's nothing in the ITR head that will give it an advantage after both are fully modified.