Bounding Box
I suspect that this isn't the answer you're looking for, but here goes…
Since I always have to make adjustments to imported .EPS frames in Ventura,
I've always taken a pragmatic approach to calculating bounding box limits.
I print the PS program, get out the ruler, and start measuring from the
bottom left. After multiplying inches by 72, I've got the coordinates. I
add the limits to the PS program, rename the file .EPS, and fine-tune/crop,
etc., with Ventura (which I'm gonna do anyway). Granted, not elegant, but
(1) it works and (2) it's fast. I'll be watching with you for some more
cerebral answers.