Hello OldSchool
Coincidentally there is no closer match to these particular original Hoshino made t rods then the seventies Slingerland T rods they look pretty much identical to one another
I do not think the threads are alike and if they do indeed ..thread right up?
Either the swivels have been changed to Slingerland on the incomplete side of the drum?
or they are the actual original Hoshino stuff you need and not Slingerlands?
I would try to carefully see if one of those known Slingerland rods fit on the completed side ...if they do?
then perhaps all the swivels have been changed to Slingerland
I really do not think Hoshino used a standard thread but I could not say for absolute certain ether
as to availability John was correct when he mentioned the Hoshino stuff being sometimes tough to find
Finding a whole distressed Hoshino bass drum may be easier than the 8 rods alone
Hoshino also used a T rod very similar to the Star made faucet handle Slingerland clones
But those would not look right and are just as hard to find
on top of that they are a lot more brittle in their old age than the Star versions
and you would need all 16
It may be easier to find five more player-grade Slingerlands to close in that side
Also and this answers a question of yours from above ...since Hoshino obviously cloned the seventies Slingerland T rods
I would fix both our kits as having been produced sometime in the early seventies not the sixties