The 360 motor and the 460 motor are completely different animals - the 460 sits further forward in the engine bay , and the crossmember gets in the way a LOT more.

As for taking all FOUR bolts out that hold the mount bracket to the frame, that's crazy. There should be a single BIG nut on the inside of the mount tower. Loosen/remove that guy, and the engine and engine mount should lift up without messing around with taking the towers off the frame.

EDIT: Yeah, I missed that it was a factory 2wd 460. I didn't know those mounts/towers were that different from the 4x4 towers. However, after looking at them, there's probably one large bolt that runs through the mount, holding it to the tower. Just pull that on each side, and it should lift right up

-Brad

P.S. - The following link shows the big stud I'm talking about: http://broncograveyard.com/bronco/i-...Fa59Ogodxn0AEw

There's a big nut (like 7/8" or something) on that stud - pull that off both sides and the whole motor should move around real easy!