There doesn't appear to be a plan showing the position of the major components in the official reports, although it would seem essential for a thorough investigation. Interesting that no such document has shown up in the records.
The four engines are probably the most concentrated blocks of mass in the entire airframe, but they are not that large when cowlings and accessories are stripped away from them.
The ground was relatively soft, so all the engines were probably partially buried in ground that was pretty chewed up by the crash and response vehicles. I don't think it is too much of a suprise that it took a couple of days to get everything found and mapped out.
I suspect only the wing tip broke away in contact with the embankment and perhaps one engine on first contact with the ground beyond. The remaining engines separated more or less together at a later stage of the impact sequence. That would account for them all being found close together, with one engine a distance away.
I'm pretty sure there would have been a lot more damage to the railroad track and embankment if an engine had made contact at that point.
If an engine had been left on the railroad tracks or the embankment, that would have made for a terrific news photograph. Someone would have documented something as dramatic as that for sure. So the debris on the railroad track is most likely bits of wing and perhaps a propellor tip.