If you take a look your first picture you posted you will notice the top tube is on an angle if you will turn it around where the angle is facing up at the motor it will work better.

Here is the engine stand I use for building motors... it has a rating of 2,000 lbs... works great for weird engines that don't have a big flange to grab onto... But I built two blower motors for my boat on this... and even adapted it to hold the speedmasters while I disassembled them to put new seals and shafts in them.... Unfortunately.. most people don't want to spend $1500 for a stand.......