Coolant Fitting Conundrum
 

I was ready to redo my coolant line routing from its "get the car running" form but I seem to have hit a snag. Previously I used 5/16 fuel hose for coolant routing. I want to do Banjo > AN > Pushlock Hose > Coolant Nipple. I read somewhere to use -6AN for the coolant hoses so I got some banjo bolts to -6AN fittings and some -6AN pushlock hose: Fragola Performance Systems Series 8000 Push-Lite Race Hose 806006 - Free Shipping on Orders Over $99 at Summit Racing

The I.D. of the -6AN hose is 3/8" and it appears the large end of the coolant nipple is 3/8" so it slips on far too easily. I can't see how this could be leak free. I would step down to a smaller pushlock hose but that would be -4AN which is 1/4" ID. 5/16" hose was a struggle to put on, there's no way I'll be able to fit 1/4" hose.

It seems I would want -5AN hose with -5AN fittings but it seems that is not a common size (if it even exists at all). Should I get a 3/8 to 5/16 adapter and call it a day? It'll look janky as hell, but I dont know how else to do it. Unless there's some way to make the 3/8 hose work?

I've heard 5an mentioned in the internet but I don't think it exists, working with piping and hosing as a profession I've never run into odd numbered an or ms fittings.

My plan (for that reason) is to use braided lines near the turbo and a 6an male to 5/16 male barb. They make an fittings with compression fittings to mount it directly to the barb but I don't want to mess with the barb.

-3 and -5 are specified, but I've also never seen them in real life.

https://www.anplumbing.com/an_thread