MPC860MH is a specific device, it supports "Multichannel HDLC" microcode, as described in
"MC68360 QMC Supplement to MC68360 and MPC860 Users Manuals"
https://www.nxp.com/docs/en/reference-manual/MC68MH360UM.pdf
If this functionality is used in your design, than you have to select any currently available MPC860, where this functionality is supported (MPC860 User Manual states that it is not supported in MPC860EN and MPC860DE).
Other differences between currently available devices and MPC860MH are:
MPC860DP and MPC860DT have only 2 SCCs, whereas MPC860MH have 4 SCCs
MPC860SR does not support Fast Ethernet Controller, MPC860MH also does not support this function
MPC860T - reduced version of MPC860P (which is superset of entire MPC860 family), with reduced cache size only
so, the answer depends on which functionality is actually used in your design. To be on the safe side, I recommend using MPC860P device, which is superset of entire MPC860 family, full-featured device with Multichannel HDLC support, 4 SCCs and maximum cache size. The example partnumber is MPC860PVR80D4 - MPC860P in lead-free package ("VR"), with 80Mhz maximum core frequency, silicon revision D4 (most recent).
