FLM Emaxx hybrid bulkheads / Ofna hyper 7 diff install problems

OK, Heres the issue. I have a set of FLM hybrid bulkheads and a set of ofna hyper 7 diffs.

I took the ofna hyper 7 diffs apart and put the outdrive shafts in so the front axle driveshafts can hook up but after assembling I have another issue. The pinion shaft that comes out the rear of the front bulkhead has a flat spot on it instead of a hole through it so I can't use the steel center shafts that came with my FLM Emaxx which is part of this project as well. I'm speaking of the shaft that goes from the front axle to the transmission.

I'm wondering if anyone knows or is aware of where I can get a pinion that is 13 tooth and the teeth are spiraled so they'll fit the 43 tooth ring gear and the teeth will mesh properly ?? Any help would be greatly appreciated. I'm not expecting a quick response as this is something the more advanced rc guys are doing so it may take some time I'm figuring so hopefully I can find something soon so I can figure this out. It's like a blockade keeping this project from moving forward.

Here's some photos so those who are interested can see what I'm referring to.