You linked him back to a thread He started =D> 8)
The 258 brackets and the V8 brackets look very similiar dimensionally. i had the same question when i recieved a set of used mounts i bought from someone. When i opened the box, I was on the phone immediately asking him what the hell he thought he was doing sending me 4.2 brackets. He assured me they were V8 brackets and after seing some pictures on this site and carefully measureing, they were correct.