Chev rear engine mount photos needed.

[Lynn Eades]

Rod with regards your question in post #4.
Here are some thoughts;
Maybe the reason for the bolt going from top (early) to bottom stemmed from the idea that it is better to have the bolt head at the top, where gravity tends to assist in keeping it (the bolt) in place. (if the nut falls off, which is better that loosing the bolt, when the nut falls off, from the top)
Then maybe, because of damage to the bolt (or an important mechanics head) and with ground clearance a consideration, a wise GM engineer (ex Ford)decided that with a castle nut and split pin, the bloody thing can't fall off, "so we will fit them the other way up" (good stories have happy endings)