I believe this engine has the one piece rear main seal crankshaft setup and has no real crank extension from the rear of the engine. If the crank was bent it either would not run or would leak oil terribly. I suspect the thin stamped steel flywheel may be bent and the runout is causing your vibration. Just remove the cover behind the oil pan so you can see the flywheel and torque converter and see if the unit is shaking. The flywheel is not expensive but labor can be pretty steep to do the change. Slim possibility the balance weight that should be on the flywheel has come off, not likely though. The rebuilt engine would no doubt outlast the vehicle, if you decide to go that route.