Hi Joe–The fossil horse limb that you found is very nice. It has the hoof and side splints. Unfortunately, it is difficult to tell for sure without the wrist or ankle bones–which are indeed very diagnostic as to front or back. The central metapodial (top center) does not look right–its end should be rounded with a central ridge. For the placement of the sesamoid boes, we would need to look at a vet anatomy text or a paper by Camp and Smith 1942 (Univ of California Publications Geological Sciences)–I do not know if these are digitally available on-line.