Some perspective...I could lift and carry around a W123 tailgate with glass that was off the car. There is no chance I could have removed or installed it alone. Working with a cherry picker may work; but, I'd redundantly secure every lifting/rigging.

The challenge will be getting the opening angle correct to start the hinge bolts and preventing sway/swing. Try using twine in one bolt on each side to try to pull the holes close to alignment and then push a tapered punch into the hole with the twine to start the alignment. Another way to start alignments is to use the longest bolts or threaded rod that will fit started in one hole. I think it can be done with persistence and ingenuity.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer