I think this would be a good choice.  Looks like it bolts right in.
http://www.speedwaymotors.com/Trans-Dapt-4037-Big-Block-Ford-to-1953-1964-Ford-Pickup-Motor-Mounts,5124.html

There are instances where a center mount crossmember is put into place on the earlier Ford pickups to use some of the later model automatic transmissions.  Here’s the link to a crossmember that can be retrofitted to work with the Y engine.
http://midfifty.com/item.php?INV_ID=1789

Lorena, Texas (South of Waco)

Re-mounting? be more specific, they came with a Y, what are you trying to do? change trans bell?

55 Vicky & customline

58 Rack Dump, 55 F350 yard truck, 57 F100

59 & 61 P 400's, 58 F100 custom cab, 69 F100, 79 F150, 82 F600 ramp truck, 90 mustang conv 7 up, 94 Mustang, Should I continue?

The standard way a Y block is mounted in a '56 F-100 is with a single mount at the front of the engine and two mounts on the bell housing to a rear cross member on the frame.  I don't know of any other way to mount the engine and transmission into an unmodified F-100 frame.

Looking at options for remounting the y block in my 56 f100, who's done what or what have you seem?