Today's adventure... after weeks of soaking in penetrating oil I finally got the old flex hose off. The differential end came apart well enough, but the frame end was truly stuck. As I replaced he hose I realized that the drivers side of the connector block is the high side, which is where the bubbles go. And this is why bleeding the drivers rear first seems to be more effective. After a gravity bleed of the hose hanging from the frame I connected the brake lines on top of the differential. Gravity bleed continued. Once connected, and the master cylinder refilled, I did a one man bleed using the left rear only and all the air seems to be out of the system.
A couple of quick photos for posterity.
A test drive showed slightly lower brake pedal effort, but not the improvement I expected. I think the rest of the brake hoses will be replaced soon.
And here is the old flex hose. The date code is June 1987. What I thought was deteriorating rubber was in fact undercoating. Really. Probably should have had a little more light under there.