While I don't have any Outlaw figs to go with this at the moment, I thought it might be useful to see some other Wild West Exodus minis next to the Flame Truck to show scale.
I think this matches up pretty nicely!
The Interceptor on the left has a rider that is the exact same size/scale as the gunner on the main weapon of the Flame Truck.
Chasing down the Lawmen!!! Dad gum Outlaws!
You really think your shootin' iron's gonna hurt that truck?
We've got ya surrounded! Come out with yer hands up!
Uh... maybe not.