You can bleed it again the same way you do on the bench, hook the tubes up to it but use the brake pedal instead of a dowel rod. This is almost exactly what happened to me, like I said got a new MC, brakes were okay, drove the truck some went to the floor again, found leak at MC got another MC, to the floor again finally got a good one and brakes have been great since.
The mc didn't come with tubes just plugs. It does say to install and test pedal before hooking up lines, so it'll get a little more bench bleed. then it says to push the pedal and crack the lines one at a time until it's all fluid and no air. Then bleed the rest of the car.
It's still not right. Got a good bench bleed and did it again with it installed. Before installing the lines the mc felt rock solid with the plugs in. Then I installed the lines and cracked the lines and pushed air out at the mc, then I bled the brake system. The brakes do work but the pedal still sinks too far. Feels good bleeding but sinks when you start the car.
Sorry this reply is so late. Hook up the lines, snug them down, have helper pump pedal 3x and hold. open the front line, just crack it, wait for air and dribble, close. then 3 pumps on the pedal, then the back line, go back and forth between them till no air.
Definitely can't get my toes under the pedal, it almost touches the floor. They seem to work ok at low speed in my neighborhood but I don't feel like I could panic stop. I have to bed those new pads still too so that is affecting feel a little. The front right caliper was wearing unevenly and that's why the pad separated, it must be sticking. Could that be bad and not leaking? It flexes a little like it's working when bleeding.
The brake light sets and resets all the time. If the prop valve was set wouldn't that lock out half of the system? I just drove it and did bed in stops for the new pads, it stops but the pedal goes too far and it doesn't feel like it stops hard enough.
I replaced the RWAL hydraulic unit today and I've bled the brakes til no end. It almost feels driveable just low pedal. I noticed bubbling in the m/c when you push the brakes. Only on the circuit closest to the booster. I can bleed all four wheels still and i can hear or feel the brakes actuate when the pedal is pressed.