Hey unfamilia thank goodness its not the case. They are are not a scaled down version of suzuki at all but as mentioned the SR20 but with the ga16 head design :) even better than the suks!. They are available in the same sizes as the suzuki G series twin cam and actually even bigger.
The micra is available in a twin cam 1.4 litre in the last years where suzuki g series dont have a true G series based twin cam above 1.3 unless you use the sohc g16 block and swap the heads to make a hybrid which is going backwards as the sohc 16v g series is better in valve sizes and port shapes.
Also the only solid crank version (no hollow mains) remains the 1.3 versions.

The micra is a bullet proof engine that as mentioned with xhausts mods will match and even outdo many similar 1.6 engines. With boost now some are almost hitting 300hp and increasing. NA race version hitting over 10k rpm all day and speedway adopting them soon they are special.

The main thing to remember is that datsuns are light and the running gear to be replaced should be the same. At around 80kg dressed and under that in race trim how can you go wrong?.