904 won't turn?

Trans is smashing your converter to your flexplate. 99.8% sure the converter is not seated in the trans. When unbolted the converter should spin freely when the bell housing is completely bolted to the motor. If you have The trans bolted up and no bolts in torque converter and cannot spin it by hand this is your problem. Unfortunately your front pump is most likely trash....

There is 2nd possibility, if the snub nose on the converter is not seated perfectly in your crankshaft (missaligned) this will also cause a binding, which may not of taken out your pump but you need to carefully back off the trans, remove your t/c and inspect for visual damage

and to make ya feel better, we've damn near all done this at least once. Sorry man :(