The motor in a Mini mounts under the radiator support on one end and the clutch cover under the other end.
The Morris 1100 motor mounts are attached to the plate behind the timing cover and the same mount as a mini under the clutch cover.
You can mount an 1100 motor in a mini by changing the radiator support bracket. You do not need to remove the 1100 mount. It does take up a little bit of room but it will fit. If you have an oxy you can cut the ears off the mount.
The gearchange on an 1100 mounts differently to a mini and the gearchange is longer. So you cannot really use the 1100 gearchange. (but some people have!) You can change the diff housing from the 1100 one to a mini one as long as it fits! They can be machined a little differently where the bearings fit.
I would use the mini gearbox.
