Now that you mention it, I do see some flats in my mounts. However, I got out the Energy Suspension mounts that I’ll be installing and they are perfectly round. I can’t see how making a mount not spin could be that important. Maybe it was a feature they put in to make the mounts a little more of a “press fit” at the factory so they wouldn’t fall out at the assembly line? My opinion (for what it’s worth) would be that the flats aren’t important for our needs.
I think you're on the right track, @n8in8or with that assembly thing. I was thinking that they were there to keep the bushing from spinning when the nut was being tightened down with a break-away impact socket as it came through that station on the assembly line. Aftermarket wouldn't need it because they're being installed with a wrench to back it up while the nut (or bolt if done backwards) is torqued down.
Thanks Nate, that means alot coming from you. Now my next dilemma, minor one, should I use steel with a rounded corners or just use a piece of 4" C channel for the rear cab mounts? I know most won't see it but I'll know it's there.