Yes those are Oem fender cowl braces. Good eye.
The edge of the inner splines that mate with the axle is what needed beveled. Basically the c-clip expands once the axle is fully seated in the gear. Without the bevel, the c-clip has no way to compress to allow the axle to be removed.
As for the m-tech, I bought mine used. I believe m-tech is now 4H-tech. I believe they’ve discontinued the shifters for the jbody.