[Arran]

With regard to the speaker hardware, you could try what they used on RCA/G.E speakers from 1930-33, which had a series of socket head (hex) machine screws with nuts and lock washers on the other side, around the perimeter of the basket. The combination screws don't look too bad, but straight out Phillips ones are just too modern, but what would be even worse are those cap screws that require an Allen key, those are mostly used on modern bicycle parts and some aftermarket car parts.
Regards
Arran