To further this; I've saved every faster I've ever pulled off Datsun and not just be cause I'm cheap.
By trade I'm a Buyer, although I now write contracts, once upon a time I worked in manufacturing. The Chinese are capable of making good quality fasteners the issue arises from the way their business works, they often subcontract and those subcontractors in turn sub contract. We has consumers have no way of knowing what was done.
For non critical low stress stuff any old fastener will likely do but for critical stuff buy known quality (Nissan etc)
Back to the topic at hand; as I've saved up bunches of bolts I routinely scrounge through the bolts bins (I try to keep similar lengths together). I know I've mixed and matched lengths on the tranny to engine mounting bolts (fortunately it doesn't seem to be an issue) Of course I sometimes manage to mix in a SAE fastener and spend 2-3 minutes trying to figure out why the thread won't start, usually when I'm contorted in a awkward position.
I just discovered today I do not have an alternator bracket for an A12, I'm currently running a faabricted piece that works but I'm not crazy about it.
D some of the weights are taken from Nissan manuals and 1200.com I believe the 80lbs on the 60 series may be wrong I think it's more like 60 but that's what I found.
I will be coming back to the post and correcting weights as I get a chance to actually weigh various components myself.
There are some weights that are semi educated guesses like the bare shell at 400lbs. That one was based on some member input.
There are others like the Cressida caliper which while lighter has few choices in pad materials; fine for street but not so much for track work.
Then there are others like the fiberglass trunk lid that saves a mere 4 pounds.