If your name is not the name on the vehicle documents, or a lien-holder is shown, you should carry documentation to cover the discrepancy. We were held up getting into Morocco and Turkey because to get around EU regulations, our german motorhome is registered and insured in the selling company's name. In both cases I was able to talk my way through using the original receipt written in German but even that nearly failed because the receipt didn't list our passport details. Had the same problem getting into Mexico with a different vehicle because we own the vehicle via a Limited Liability Company.
As Chris suggests, you don't need much documentation to satisfy customs that you have a legitimate right to be driving the vehicle and I have used a DIY version a couple of times, but given the cost and time getting all the way down to Morocco and the chance of striking an official with good eyesight having a bad day, it might be worth trying to get an official letter from the lease holder.
An alternative precaution is when you book the ferry ticket, the agent usually fills out the import documentation for you and if they add your name as an owner as well, the customs officer will likely accept it without question (as that is how I got in. He pushed the paper back to me and said I should add my name in the owners box and then he was happy)

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Tony
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