Here is a rough drawing with some dimensions on it. I adjusted the cab basket rail back 2" to allow for your light bar. I'll let your fab guys come up with a design for the lights. I'm pretty sure this should give them enough to go off of. Good luck with it. You'll have to show us some pictures when you get it built.
FYI... I didn't know what type of material you are going to use. I just picked some basic tubing to use in SolidWorks. You can have your shop use whatever they deem necessary. They will probably make some changes as necessary to help with rigidity and support. And, just to be safe (because you never know in today's society), I'm not liable for any damages after this point.
I'm not an engineer, so don't hold that against me.