Hey Jeff,
All the drawings I've seen with the continuous draft gear shows the rod at 1.75" and attached to the link and pin coupler housing (?) as shown:
D&RG 30' boxcar 1888 (colors added to highlight)
Not sure if this was the 4000 series or not, but this arrangement seems pretty common on early stock cars and gon drawings that I've seen.
One thing I hadn't realized until today was that the rod was sandwiched between two extra center sills which are in turn between the two center sills we normally see on later cars:
(section from same drawing)
This section shows a circular groove but I've also seen a square channel. There was also a turnbuckle located along the rod somewhere in the middle (position varies) and accessible for adjusting.
I assume that with the advent of automatic couplers in the teens that the rod became obsolete and was removed along with the two interior center sills I would think, but just guessing. No expert here, only see what I see.
Not usually my era of choice, but finding early rolling stock tech to be way cool.
Mike