318 to 360 swap

The mount itself came loose because of not being installed correctly.
well, I have no idea who did what and what you saw happen to who. Don't take this personal, take it as constructive criticism - IF you understood how using a spacer in the mount worked you'd not be at all stating the things you state. I have two cars right now using 318 mounts on 360's using spacers, not to count all the times I have done it in the past, along with hundreds of thousands of other mopar people. The only way I'd "buy" 360/340 mounts instead of using a spacer would be if it was a professional restoration or I found the mounts for 5 bucks.