You can't legally sell that which you don't own, and you don't appear to own the vehicles.
Was your father's estate probated, with the titles to the two vehicles transferred to you? If not, then you can't legally sell the vehicles.
If title has been transferred to you, then you can sell them, but any sale will be subject to the liens, and no intelligent buyer is going to pay full value for a vehicle subject to a lien.
You can keep possession of the vehicles until such time as someone challenges your right to do so. If the liens are there to secure loans, then one would expect that the bank will repossess the vehicles if the loans don't get paid.