Bad Hadraulic Lifters, Maybe?

I have been playing with this lately after changing cams and needing to change to a brass gear for the oil pump drive shaft. With the oil pump installed the oil pump drive shaft will engage the hex before it will engage the cam gears - I think. Sure feels that way cause you can turn the oil pump with the drive shaft before the gears engage. That is good because then you can align the gears the way you want and the hex is already engaged so it is not interfering. I can see where trying to force the drive shaft down with the hex not engaged properly might cause the damage to the pump drive that you showed. I am just guessing.

Something wrong with the brass gear drive shaft (M..n or M..o?) design? The all steel shaft I took off didn't have a pin attaching the gear to the shaft, the new brass gear design does.

You guys ever try to put the dist into the oil pump drive gear outside the engine to see how tight/loose it is? The blade on the MSD dist I had been running would not fit into the hole on top of the oil pump drive brass gear - the damn hole was a little too small! I ended up having to gring a little off the sides of the dist blade on the tip of the dist shaft and drove the dist into the oil pump drive. They are now a nice tight unit and that is how I discovered that the hex of the oil pump drive would engage the oil pump before the cam gear - when I was indexing the dist/drive assy to get the rotor pointed where it is supposed to be. If I had not tried to check that fit, who knows the damage that may have occurred when installing the dist with the oil pump drive shaft already installed.

I think you should always check new parts for fitment.

Sorry to hear about your issue - like MRL says, not good to run without oil pressure. Can you pull some main and rod caps to look at the bearings / journals?

Oh, as for the lifters... My stroker was built, dyno'd, then put in a bag for 3 years with the rockers still bolted on tight. I got it from the PO and put it in my fish after doing the oil prime routine. Ran great but kinda had hard starting issues. When I took the motor out and was unbolting the rockers for storage I noticed that some of the lifters had soft plungers (Comp hyd). I think they collapsed from having the valves open so long and the main springs overcame the light lifter springs. That may be your problem with some of the lifters being squishy.