I don't have a picture but someone probably does. I remember (I think) Granada brakes being mounted on the wrong side where it makes the bleed valve not at the top. If you mount them on the wrong side you will never get all the air out due to the bleed valves not at the top. Not sure if this is your issue. I'm not a brake guy but a trouble shooter. Another thing I would try is put a plug in the master cylinder on the front and back brakes, one at a time. This way you can tell which is causing the problem. I don't thing it is the proportioning valve.

15” brakes sounds like might be four or six piston calipers?   Did you bleed the inner and outer half of the calipers independently?   Typically are two bleeders per caliper on Brembo and the later Ford big calipers.