Power steering gearbox - what thread/flare size?

[RustyPile]

I realize this is a 14 year old thread that someone resurrected from the dead.. I just finished installing power steering in my '71 C/10 where previously there was none.. The gear box has inverted flare nut threads.. Do Not, I repeat, DO NOT try to install NPT fittings.. You will ruin the threads in the gear box rendering it totally useless.. For the return line I used a piece of "premade" 3/8" steel brake line about 9" long.. Using a tubing bender, I put a 90 degree bend in one end as close as possible to the flare nut.. Be sure the flare nut is against the flare before making the bend.. I cut about 1 1/2" off the other end and removed the other flare nut.. Using a double flare installing tool, I put a "bubble" on that end of the tube.. I Then installed the return line fitting onto the gear box. I bought a piece of bulk PS return line and connected the steel line to the PS pump return line fitting.. Use fuel injection fuel line clamps, not those screw type clamps.. The pressure hose I used is Edelmann's part number EDL-70911.. Everything is available locally, no need to mail order anything..