the rear tailshaft flange from the later jap assembled 120ys(h150) are the same as the 720 one. same with h165 flanges

R31 brakes are probably as better option to make fit the rear as they have a steel bracket so its a bit easier to mod than the alloy bluebird one
or vn commdore ones for that matter as they are pretty much the same thing but with a larger disc and more caliper offset