[Second Series]

The parts store had a F-F adapter with M10-1.0 and 3/8-24” so with that I was able to confirm the brake line from the ’88 is 3/8-24” and the brake line from the ’95 is M10-1.0. (I hope I didn’t get that backwards). They didn’t have the adapter I need so I ordered one for each end. I’ll bring the lines to confirm when the parts get in to the store.
When I removed the line from the brass T, it was snug, so I must have use a heavy hand to install. Makes me think that end is metric on the line fitting. This used line accepts a 14mm wrench and a 9/16” wrench is loose. The old line from the ’88 accepts a 9/16” wrench and the 14mm wrench is too small. I checked the line on my 1990 k1500 and found the 14mm wrench too small, 9/16” wrench fits. Then I looked at the ’88 k2500 at the brass T the fitting from the driver side line does accept a 14mm wrench, but I can’t confirm what the threads are. I looked on-line some more looking at the hose since there is specs listed for that, and every listing shows 3/8-24” where it connects to the line, and 10mm at the banjo that connects to the calliper.
This front line is 7’ long with over 20 bends, the used line that I bought does not appear to be cobbled. The O-Reilly’s website has a listing of every vehicle the one part will fit on, it looks like they were all SAE, but I couldn’t locate a metric brake hose. LMC has three listings for the set of brake lines: 88-89, 90-94, and 95-98, but no specs.
The local parts stores don’t seem to carry a pre-bent line, only straight pipe with fittings, and only up to 6’. Or I could get a roll and flare the ends. The on-line retailers that do sell pre-bent lines only sell as a kit, and they don’t list the specs, so I can’t tell if the fittings are metric or SAE, just that they fit my vehicle. 3/8” = 9.53mm (.3750”) and 10mm = .3937” so the 10mm fittings will screw into a 3/8” socket.