I don't know what an SR-71 is, but I bet its not as cool as this. It reminds me of the jet fighter/spaceship hybrids in classic video games like "Defender" and "Gradius." I like how you used the old castle corner peices as well. Very Nice.
I love the detailed engines (or is it thrusters?--I'm talking about the circular and semi-circular pieces at the very back). Odd though, it has a liscense plate but no brake lights.