I don't know who built it but can tell you what part of the country it was mostly likely made. The blind fastback seat stay treatment was popular in mid California in the last part of the 70's and maybe into the 80's. I would guess somewhere in the Bay area. Of course it could have been built anywhere but I distinctly remember that style was most common in CA. Henry James investment cast lugs started to be popular starting around 1980. Those look like Prugnat lugs from the 70's.