360 magnum into '66 Valiant

The mount needs the same modification that's necessary for an LA 340/360 swap. For the passenger side mount, refer to:
Motor Mount Bracket - dwg I.jpg (600×800) (cloudfactory.org)
On the driver's side, a 5/8 spacer needs to be used between the upper rear engine mount ear hole and the bracket.
To fit a 727 to an early A, all you need is a BFH. The pinch weld needs to be folded flat, and various clearances may need to be "enhanced". Different As may need more or less work- they're all different.