All I can tell you is with the Dataradio stuff I could pull a full 56k going 100mph while riding between two mountains in MT.  you just need diversity Rx and really good fec.  These were using Z80 processors on 25k channels.  with some work I am sure a protocal can be modified to do this and more.  Remember Dataradio was founded by two of the hams in Montreal who developed ax25 in the 80s.