I don't know, I've worked with AN fittings for years up to 1' in size (16) with few problems. I've never had to resort to doing anything other than making sure that both faces were clean with no burrs. As to mixing and matching SAE 45 degree fittings with AN 37 degree fittings, I don't think the nut threads are compatible enough to get this done. Don't know though, never tried it. This link is an excellent discussion on fittings.

http://www.malonespecialtyinc.com/tech.htm#anchor136590