I have done a Similar conversion to my R34, execpt I bought a whole written off R34. Took all the parts that I needed and sold off the parts that I didn't use as well as my old engine/box.
I didnt really keep track of the exact costs, but my whole conversion wouldn't have owed more than $2500 (Including new clutch, Timing belt kit, Brakepads and rotors)
I thought it was a much better option than selling up and buying a GTT as I already knew the condition of the car inside out.