Where in the Mission was this taken?

In 1970, San Francisco rock and roll band The Grateful Dead released an album called "Workingman's Dead."  It did moderately well, eventually reaching #27 on the Billboard album chart and was certified gorld (i.e., 500,000 copies sold) a few years later, in 1974.  Even if you don't especially like the Grateful Dead, the album is essentially harmless, a pleasant collection of stoner country-rock that makes a perfect accompaniment to a Sunday morning making brunch after smoking a couple of bowls.

The cover photo of the band was taken somewhere in the Mission District of San Francisco.

Here's how Blair Jackson, Jerry Garcia's biographer and a longtime writer about the Dead, described the shot:

Artist Alton Kelley says that the title and concept for the cover was his: "I wanted to make it look real utilitarian," he said. "We took the picture with a little Brownie. You couldn't get that funky a photograph with a good camera. We went out intentionally with an old camera to do it. They stood on that old street corner somewhere in the Mission District [of San Francisco]. And they were bitching and griping about having to stand out in the street looking like that, getting their picture taken. That's why it came out so well! Billy got so pissed off he just went back and sat in a doorway. We were at a bus stop and he was actually going to get on the next bus!"

Yesterday, whoever the shadowy, mysterious figure is who runs the indispensable SF_Historian Twitter account wondered if anyone could help him locate where the shot was taken.

Treasure hunt: can you identify where in SF this picture was taken? I've tried and failed. Likely Mission/Castro area: tinyurl.com/akc9n8p
— SF_Historian (@SF_Historian) January 24, 2013

No one's figured it out yet, although some good additional information has come to light, like this photo from the same session:

What are those things over on the left?  They look like gas storage tanks to me.  Pastmapper suggests that the tanks will be found in this 1968 aerial photo of the Mission.  Feel free to put on a loupe and scan away, my marginally employed friends!

Some people have suggested that the corner doorway looks like the Homestead at 19th and Folsom, but I'm not convinced.  The rest of the wall looking down 19th doesn't look like it, and that Victorian house doesn't match.

We should also point out that this guy is so into this problem he bought a Muni map from the 60's and then followed all the routes on Street View looking for it because of the bus stop part of the anecdote above.  So far, no luck.

So what do you think, guys?  Recognize the spot?  Any ideas?  Anyone want to go out today and make an exhaustive survey of every corner-facing doorway in the Mission?

POSTSCRIPT:  Of course, the real question here is WHY.  Why do we want to find out where this picture was taken?  Well, it would be interesting to know, as a historical (or "an historical," if you're from New York) curiosity.  But I really want to find it so I can get 6 friends together and recreate it exactly, IF YOU MUST KNOW.