To be honest, I think if it was in there, it was replaced/removed just before they turned on the giant turkeys originally, so a patched copy of the client from some months before then might have the original one in it still, if it existed. You could look up patch notes to get an approximate timeframe, then do a really old install and let it slowly work its way through 'til you get to an area that would be about right.
For additional help, I can tell you i'm pretty sure the bodyconv.def entry didn't move, or if it did it wasn't much, so it definitely happened sometime after ML, and would likely place it in the timeframe of where it is in that file, between publishes 42 and 52 somewhere, or at least before the new graphic was put in for 62.
Really wish I could narrow it in better than a frame of 30 bloody publishes, but.. my memory sucks. I can say I do remember it being added in there the same time as the Time Lord and new Shadowlord entries though, but I could be remembering wrong. I also remember I asked constantly about it on the forums for a while, but never did get a solid answer either way, nor did I get any help searching for it with insideUO.
Oh.. and as to stuff "being in for more than * months generally being too late to change".. honestly, for most of the things added with LBR and SE and ML, replacing them with stuff not ripped from low res polygonal models wouldn't be too bad so long as they fit in better in the long run. For example, i've yet to hear any complaints about the changed gargoyles, and that happened just after SA. The ones you really need to be careful about are the mounts that were added with each of those (of which currently the only one with a KR equivalent that actually looks exactly like the original creature is the Ridgeback).. everything else should be fair game to replace so long as you give them the same run-overs that you did with the 2D SA sprites.