Ok good plan on paper, im not sure if it will work out, as u need to look at another factors.
1.Insurance
2. Running cost of an rb26
3. Normal running cost fuel, services etc etc
Also, getting a loan i dont think is the best idea. Im basing this apond the fact that u will have to pay off the loan and then save for insurance, fuel and then all the random bs (going out, drinks, partys, girls etc etc)
Also, dropping an rb26 into an gts-t r33, i heard isnt the easys job (something about the floor plan needing to be change or something)
Also with power comes BS stuff, like u want 320hp (which i think is way too much currently i got about 200/215rwhp in an r33 and that is crazy enough for me maybe 250-270 would be good) u up the boost something goes wrong and u blow the piston ur car is out of action untill u can save for the rebuild etc etc.
Maybe just buy the gts4 and just say with that add a fmic, ecu, exhuast, air filter (all the basic mods) and u will have enough power, and in the future when u have the money then look at doing the rb26 swap (remember ur swaping an engine the cost for the engine is around 6k + u have to add labour and all the other bs)
just my 2cents, keep saving, keep looking and i bet u will find something good enough