OK, so threads and fittings are not my thing, but a bit of google tells me some things. I think what I'm checking is:
1. That the loader has 3/4-16 UNF (or 9/16 UNF?). Which is the thread that an SAE08 port has, although I don't know what an SAE08 port is. And that should mean that the diameter across the outside of the threads is 3/4 inch (or 9/16 inch?), the F means it's fine pitch. The 16 I think refers to the number of threads per inch - so on a 1 inch bolt I should see 16 threads (the bolt is roughly 1 inch). So I could measure all that if I can dig out my calibers. 3/4 would be 19.05mm, 9/16 would be 14.3mm. The loader port is bigger than the tractor side, and I think below I decided the tractor will be 16.6mm. So it's probably 3/4 on the loader.
2. I think you're saying that there's no actual need for a banjo, and I can just get a screw in fitting in 3/4-16 (or 9/16?) UNF, that the hose shop has the right fittings to connect to the hose.
3. Next, you're saying that the tractor side port is BSPP. I don't know what size, I see you mention G3/8 - that's 3/8 inch? And Whitworth .650 - 19 would be .650 inch with 19 threads per inch? So I think that means that BSPP uses Whitworth thread sizings. Why on earth do people mix decimal measures with inches? And that can't be right, because 3/8 is .375, not .650, so I'm very lost there too. I can measure it though and tell you.
Wikipedia says there's no Whitworth 3/8-19 (
https://en.wikipedia.org/wiki/British_Standard_Whitworth#List_of_thread_sizes), but it does point to BSPP, and BSPP has a 3/8-19.
https://en.wikipedia.org/wiki/British_Standard_Whitworth#List_of_thread_sizes. It says a major diameter of .6560, or 16.6mm (my calipers will be in mm). So I think I can measure that.
And I think that the page says that the 3/8 has nothing to do with the thread size, it's the inside diameter of a pipe that had an outside diameter of .6560 inch. And even worse, the pipes no longer have 3/8 inch inside diameter, because they have thinner walls nowadays, so the 3/8 refers to a hypothetical inside dimension that isn't the real inside dimension, and has nothing to do with the actual thread size. And people wonder why the rest of the world moved to metric!!
I went to the Kubota dealer today, the most knowledgeable guy there said that those fittings are all odd/custom sizes, and basically it means only OEM parts fit so far as NZ is concerned. He can order me another pipe if I cut this one, but it comes from Japan and it'll be about a month.
I'll ask the hose guy if he has any ability to access the fittings we're talking about, but otherwise I think I'm back to cutting the fitting, because I know that'll work.