Many times when I get problems like that I go around and block off the lines to the calipers as RapiRobert said. In a hurry you can use needle nose vise grips and block off both front at the same time. Then switch to the rears if no better and see if you get a good pedal like that. If the pedal gets solid by blocking the front or rear then block just one to see if its both or one side. Many times in conversions I see like Feets said that the bleeder on the caliper is not high enough and wont always get all the air out. But blocking the caliper lines will tell you if it has air stuck in a caliper. If I do the front and back and still no pedal you can do all 4 and see if it gets a pedal to know if its a problem in a front and rear caliper. I have found many problems like this including a Ford that had the calipers on the wrong sides and that caused the bleeders to be to low and would not bleed all the air out. Good luck , Ron