Best ally for Ork Speed Freaks?

[scrotatohead]

My son has a pretty good core Ork army that would be great for speed freaks (6 x bikes, battlewagon, couple trucks, a buggy), and I've got marines bits I can convert for additional bikes, buggies, looted wagon, etc.). I'm going to take it off of his hands because he's just not into it. I don't want to go all-Ork though. From your experience what is a solid army to ally with a speed freak list and why? Do you go with an additional fast army like Eldar so that everything is in the enemy's face? Or do you go with a Tau gun line to provide wicked supporting fire? Or Daemons for FMC support? I'm open to all suggestions. Unit/model examples would also be helpful.

[Jabberwocky]

Beyond apocalypse, I find ork allies awkward for anything beyond Tau, where they could be mercenaries.

From a gaming point of view, those 2 should compliment each other quite nicely with some long range fire support and a bit of skyfire.

[baconslice]

Yea tau are an easy obvious choice. But you've kind of answered your own question. It just depends what you fancy. Fun, fluff or power?
I do like the idea of speed freak eldars.
You could have wave serpents and warp spiders zipping every where. Jet bikes and a wraith knight just incase
Quite a cool concept and not exactly under powered with a good build.