Yes you should appoint proper parts inside 3dmotion for each mount you have in game...
here is an example of part for 1 mount - ShadowKnight skills covering:
Part taken from official...
000097001480780=c3/0001/480/780.C3
000097001480781=c3/0001/480/781.C3
000097001480782=c3/0001/480/782.C3
000097001480783=c3/0001/480/783.C3
000097001480784=c3/0001/480/784.C3
000097001480785=c3/0001/480/785.C3
000097001480786=c3/0001/480/786.C3
000097001480787=c3/0001/480/787.C3
000097001480788=c3/0001/480/788.C3
000097001480789=c3/0001/480/789.C3
000097002480780=c3/0002/480/780.C3
000097002480781=c3/0002/480/781.C3
000097002480782=c3/0002/480/782.C3
000097002480783=c3/0002/480/783.C3
000097002480784=c3/0002/480/784.C3
000097002480785=c3/0002/480/785.C3
000097002480786=c3/0002/480/786.C3
000097002480787=c3/0002/480/787.C3
000097002480788=c3/0002/480/788.C3
000097002480789=c3/0002/480/789.C3
000097001480754=c3/0001/480/754.C3
000097001480768=c3/0001/480/769.C3
000097001480769=c3/0001/480/769.C3
000097001480770=c3/0001/480/770.C3
000097001480771=c3/0001/480/771.C3
000097001480772=c3/0001/480/772.C3
000097001480773=c3/0001/480/773.C3
000097001480774=c3/0001/480/774.C3
000097001480775=c3/0001/480/775.C3
000097001480776=c3/0001/480/776.C3
000097001480777=c3/0001/480/777.C3
000097001480778=c3/0001/480/778.C3
000097002480754=c3/0002/480/754.C3
000097002480768=c3/0002/480/768.C3
000097002480769=c3/0002/480/769.C3
000097002480770=c3/0002/480/770.C3
000097002480771=c3/0002/480/771.C3
000097002480772=c3/0002/480/772.C3
000097002480773=c3/0002/480/773.C3
000097002480774=c3/0002/480/774.C3
000097002480775=c3/0002/480/775.C3
000097002480776=c3/0002/480/776.C3
000097002480777=c3/0002/480/777.C3
000097002480778=c3/0002/480/778.C3
000097001480946=c3/0001/480/946.C3
000097001480947=c3/0001/480/947.C3
000097001480948=c3/0001/480/948.C3
000097001480949=c3/0001/480/949.C3
000097001480950=c3/0001/480/950.C3
000097002480946=c3/0002/480/946.C3
000097002480947=c3/0002/480/947.C3
000097002480948=c3/0002/480/948.C3
000097002480949=c3/0002/480/949.C3
000097002480950=c3/0002/480/950.C3
000097001480746=c3/0001/480/746.C3
000097001480753=c3/0001/480/753.C3
000097001480759=c3/0001/480/759.C3
000097001480760=c3/0001/480/760.C3
000097001480761=c3/0001/480/761.C3
000097001480762=c3/0001/480/762.C3
000097001480763=c3/0001/480/763.C3
000097001480764=c3/0001/480/764.C3
000097001480765=c3/0001/480/765.C3
000097001480766=c3/0001/480/766.C3
000097001480767=c3/0001/480/767.C3
000097001480779=c3/0001/480/779.C3
000097002480746=c3/0002/480/746.C3
000097002480753=c3/0002/480/753.C3
000097002480759=c3/0002/480/759.C3
000097002480760=c3/0002/480/760.C3
000097002480761=c3/0002/480/761.C3
000097002480762=c3/0002/480/762.C3
000097002480763=c3/0002/480/763.C3
000097002480764=c3/0002/480/764.C3
000097002480765=c3/0002/480/765.C3
000097002480766=c3/0002/480/766.C3
000097002480767=c3/0002/480/767.C3
000097002480779=c3/0002/480/779.C3
In attachmet I am putting as well example of 3dmotion that I made for DO - it covers all weapons: 410/420/440/450/453/480/483/490 (453 and 483 - are typically for my needs addiotnal ;))...
But you checking it how its built you should see more clearly whats the structure of this ;)
So generally you need to build own pattern and prepare this for all single mount (you can make already for all 100 mounts...)
Hope this will help you little out there ;)
cheers