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Taking the motor off completely is not necessary. I already had it off the second time and it is easier to drill and patch that way.
The first time, on the 1964 I ran a 2x12 from a beam in my carport to the top of a 6' stepladder in line with the top of the motor. Then used a cable puller to secure the motor. When it was tight I removed the bottom lag bolts.

Then I removed one top bolt and loosened the other so the motor could pivot on the one remaining bolt. I was able to re-insert the other top bolt one hole up at that point. Then I pulled the other top bolt and pivoted the motor to raise the second top bolt one hole. Repeated this process to raise the motor to the third hole up.

Then with the top bolts re-inserted I was able to drill the green holes with the motor in place. Slight upward angle was necessary to get holes into the splash well. It was a while ago, but as I recall the lag holes were below the motor bracket after the motor was raised.
Epoxy thickened with fine chopped glass, or a dowel and epoxy will fill the holes. I used "wet /dry 700" a fairing epoxy compound from Progressive Epoxy the second time. It is super easy to work with and doesn't run at all.