I know I should have just upgraded everything to the PBR brakes, however I had already purchased pads/rotors and new rear hard lines for the Delco Moraine rear calipers I have for my 87 Iroc. I'm having issues locating an adapter for the driver's side hard line that goes directly to the Caliper. The hard line fittings purchased from Eckler are 3/8, where the Calipers have a m10x1.5 hole size, as I had no issues attaching the passenger side with the Hose and new Banjo Bolt.

Any ideas in sourcing a proper 3/8 to m10-1.5 brake line adapter, I've tried a dorman BLF-29C adapter that a friend had, however the pitch is only 1.0 which obviously didn't work.

 

87 should be all metric. Calipers, steel lines, rubber lines, EVERYTHING.

83-back was SAE, 85-up metric, 84 could be either. Sounds like you have a mix-match of parts going on there.

 

Yea, eckler’s told me they were the correct hard lines to split off from the T. I was having trouble with that connection and reached back out and they told me the flared fitting was 3/8. So I’m not sure what to do at this point.

 

Not hard to figure out. Get the right (metric) lines from somewhere else. Inline Tube, Fine Lines, Classic Tube for example. One of those, or similar, is probably where Eckler's gets em from anyway.