We can't figure it out the just don't show enough of the car and the quality just isn't good enough. I think its a vintage rolls royce from the grill, The Mogan looks close but the lights and the back-end are all wrong.
Having watched the movie I do know a few things

1. Henry rollins is a big MOFO
2. The money martin Lawerenc finds in the coffin doesn't even look close to real.