Here is where I get all my fittings. Every size you need. I'm late to the reply, but I assume from your statement, you want -6AN to something bigger than 1/8 NPT.
Anyway.
http://www.verociousmotorsports.com/Shop-by-Category/AN-x-NPT-Adapters
Yeah my link was for reference, to what I was talking about.
M3 is sort of small, a slightly larger screw would almost certainly be better. Depending on goals.
You could also just buy a rivnut install tool... And avoid all the nonsense. Once the depth, and squeeze throw are set, stripping the insert is almost impossible.
I get you prob didn't want to wait, or they weren't available locally.
Link for reference:
I have mine ~6in from the nozzles. Everyone at the time told me the closer the better, and 6" seemed reasonable.
I mounted mine on the flat tab thing, to the left of the intake filter, if looking from front of car.
I've run it this way for a few years now without issue. I'll look at your...