I compared it to a couple original pumps. It does look like it is based on the ECG pump but it is not an exact copy. So whoever produced it must have used the ECG as a reference for the design.
The rotors are the same and the cover plate o-ring recess is the same so a Melling kit will work to rebuild, if necessary.
The bypass bore measures .558" with my caliper, so that's 9/16" bore, which is just about right to tap for a 5/8" plug, like the originals.
My observations are made with caution because the pump had already been disassembled when I got it. Two differences stand out, not including the bypass valve. One is that one of the cover plate holes is counter bored. It does not look like it has been stripped. Another is the threaded boss for the one of the three bolts that hold it to the block. There is a recess in the casting of originals, limiting thread engagement to only about 1/4". On this one, the recess is not present, allowing for more threads, which is good to prevent careless installers from stripping them, which I have seen in many aluminum pumps.
Counter bored hole, upper right hole:
Mounting bolt thread boss recess, toward the right side of the pump:
To show what I stated earlier in the thread regarding the cover plate orientation. Iron top, ECG left, C1AE right:
This helps to see the bypass valve piston stop extension of the original pumps. With the ball, that will never be in the path of the oil flow. The pistons can only move by about 23/32" because of interference with the piston and plug, which would pull it all the way out of the flow but that would only occur at the highest pressure if it happens at all.
Lawrenceville, GA