AS others have said, that rim is correct and as manufactured. Take the lock ring off. Also, take the connecting bolt out, and overlap the two ends of the rim. The tire will drop right in. Then, with a small crow bar or tire iron, spread the rim back into alignment and put the bolt in. Put the lock ring on, and put in about +/-5 PSI of pressure. Use a rubber mallet and work your way around to get the bead up against both the locking ring and the other solid rim lip.
Seating the bead on a split rim is NOT, I repeat NOT like doing a solid rim. You work the bead up onto the lock ring a little at a time, until it seats. Then, with the lock ring pointing AWAY from you, slowly bring it up to pressure, which should be around 12-15 PSI.
Have done quite a few rears that way. I have done a number of truck tires too, but they run at 100 PSI, and usually I had/have a cage made for the job. However, I have also done a few the old fashioned way, which is to point the ring away from you, and reach through to fill with air, or use a locking chuck.
In any case, you never pressure up to "snap" the bead into place on a split rim. You ease up on it, until the bead seats against the lock ring and the lock ring is seated. Then bring it up to the correct pressure.
The reason people get hurt with these is because they are lazy or impatient, and the results are the horror stories you hear.