Jason,
I spent a little time on it. I hope it is to your liking. This is what I did.
1. As mentioned before I cropped it tighter.
2. I used photoshop image adjustments (mainly contrast) to deepen the tones on the whole picture.
3. I used the Burn tool on a low (6-8%) setting to shade under the wings, fuselage, drop tanks and a few places on the fuselage. The spinner got a little time spent on it as it's a focal point.
4. Used the dodge tool, again on a low setting with a 2-3 pixel soft edged brush. This was to add highlights to the spinner, fuselage, drop tanks. Again the spinner got most time spent on it.
5. 6 pixel brush. Dodge on 8% to highlight the canopy.
6. Paintbrush on 1 pixel, 6% black colour - drew in the panel lines. Then sampled the fuselage colour and on a new layer painted some detail.
7. Paintbrush on 1 pixel 6% white colour - highlighted the panel lines.
8. Took a screenshot of a still P51 prop from the same angle, cut it out, scaled it, then used a radial blur tool to give the effect.
9 Lastly used the Render lighting tool with an omni light to put the sun into the picture (position slightly wrong..Grrr)
Oh well, this is what it looks like
