I do know exactly what those rubber vacuum caps look like as far as the way they're molded.
I just have to find the correct length to cover the stud all the way to the flange nut.
There are a number of different lengths for any given id, so the pic helps alot thanks.
There are 4 NOS in the box on eBay that look promising, but the seller doesn't reply with what tube size they're for,
so good luck with that sale!