Camera help if you will

I want to install it on the lip, from the lip to my bed is 22 7/8. Is this the best spot to mount? If I measured correctly the inside of that lip is 581.025mm from the bed. Taking that math the 120 degree camera is 466mm and the 90 degree is 500mm, so the 90 degree is the right size for me?

It sounds like the 90 would be correct, as long as the mount point is directly above the bed, not at an angle (angled mounting means a bit more cropping).

I want to mount it where the arrow points.