As seen in Forest Encounter, it's the Rebel T4-Anti-Air Speeder. A bit more toned down than its cousin, the Rebel Support/Attack Transport, it still has an anti-air turret, and features an astromech slot.
Taking the advice of a flickr member, I redid the transport using the same front and a totally different back.
The turret is exactly the same, I really can't think of anything to change it anyways.
Astro-droid slot! In Forest Encounter, it's specifically R2-D2.
The back. I just LOVE those grill slopes!
Bottom, with those rounded 2x2 discs for extra SWOOSH.