By 'better' rust treatment, it's still not great. I think it has something to do with the Datsun badge... In saying that, I've managed to accrue a couple of sets of almost rust-free doors and sundry other panels over the last 10 years so they do exist.
Mine have all been early model Jap ones (2 sedan rally cars & 2 coupes). The H165 diff (Jap diff) has been reasonably hardy - have broken the axles before the centre. Can put in the 4.11 1200 ute centre or the 4.875 vanette centre with ease for better ratios. I have Aussie struts and brakes on the coupe which for the L20 in it which is fine.
Downside with early model is if you stack it, bumpers (non-safety with the rubber bits) are hard to come by, grills also but all the mechanical bits are the same on both.