Eternal Oil Filter 1074cc engine

[JEM1]

Hi,
Note I previously posted on prewar forum also,
I have a 1074cc 10 engine for my Le Mans special. I am adding a remote oil filter with spin on filter.

From the photo below is "A" the feed to the filter and is "B" the return back to sump ?

I am also trying to confirm thread type / size for each. Looks like "B" is 1/4" BSP ? Can anyone confirm?
The "A" seams to be a different sizes and pitch, "A" appears a smaller diameter and a courser thread. Does anyone know what thread "A" is ?

Thanks