I'd generally agree that it shouldn't kill the trans pump, but after 2 failures... I'm grasping at straws here. It could be possible that the torque converter has some runout, but I don't have the equipment to check that. I'll pull the flexplate and check the oil pan alignment again. On my blazer, I may have to pull my engine cross member to get it out. I'm tempted to loosen and tap forward, but I have a feeling the RTV joints might either leak or resist moving.
The major symptom is 2 failed transmissions with low miles. Pump was shattered on the first one, don't know about the second rebuild but I lost all pump pressure. Dowel pins are in, torque converter clearance was 1/8" each time, crank end play is good, runout of new flexplate is .008" max. Not sure what else to check. My trans builder is a highly respected speed and performance guy. Very meticulous and I trust he isn't doing something wrong here. But something isn't right....