Answer to the second question: "would tow truck work?" Yes. He even made a locomotive into a time machine.
Since Dr. Brown later used a locomotive as his time machine platform, the suggetion is that the choice of the Delorean, however, was mostly style, as he claimed in the movie, not necessity. A locomotive is mostly cast iron rather than steel, and definitely not stainless steel as the Delorean is. Metal itself might have been significant to the operation, or efficiency, of the flux capacitor, possibly even ferrous metal such as iron.
A modern car, with non-negligible amounts of other materials in the body might be questionable. A tow truck, of the same time frame as the Delorean, was nearly all metal, and most of that steel (even if not stainless steel), so using one wouldn't be an issue, from the point of view of the flux capacitor. Dr. Brown's tow truck, however, might have needed more work (and investment of money and time) before being able to reach the needed 88 MPH for transition.