Driftwood,
To my eye, these are age appropriate. The designs of ancestor figures and the representation of the paipushe snake are typical of the Paiwan. You can compare these renderings with others kept in museums and I believe you will find a strong match. Not proof of authenticity, but certainly proof of careful workmanship.
One must remember that the island tribes have been substantially affected in the last 100 plus years by the arrival of large numbers of Han immigrants from China and also by the long Japanese administration. Intermarriage, relocation, and other social mingling has occurred. As a consequence, the distinctiveness of the aboriginal tribes has diminished. Nevertheless, traditions carry on.
It would be my guess that pre-Japanese artifacts from individual tribes such as the Paiwan (Baiwan) are scarce and there is scant chance of such items appearing at a local market.
but it could happen!
These do not look at all like mainland Chinese replicas. Pictures are seldom sufficient so you must judge the quality of the steel and the rest with your own senses. What I do know is I that you already have a story and also a that you are unlikely to find these weapons outside Taiwan. If you don't buy them, you will think about it for years. Finally, should you buy them and then decide you'd prefer the cash, I have little doubt that you could pass them on to another collector.
B/r
Dave A.