Acording to the RSR workshop manual Rover 14 1936 is a P2 Rover. This is what the manual says about gearbox removal of Rover P2:
“GEARBOX - TO REMOVE AND REPLACE
This operation is necessary if either gearbox or clutch needs attention and the preliminaries apply where external attention is required.
Detailed instructions are not included as the operation varies with the model, year and type of body. The basic details apply to all as the gearbox is removed inside the car.
1. Remove front seats, all carpets and gearbox cover.
2. Remove front floor boards, brake and clutch pedals and toeboard.
3. Disconnect clutch linkage, propshaft, speedometer cable, freewheel cable, reverse light wires
and any other connections (e.g. earth strap, stabiliser rod etc.).
4. Remove gear lever and disconnect support bracket (top half on 1947-49 cars). Disconnect check
strap (1934-46).
The next operation involves jacking up under the flywheel housing to lift the gearbox free of the mounting and high enough to clear the floor. To achieve this it may be necessary to remove other items such as the handbrake or floor board support channels depending on the model.
Before jacking up various items may need to be disconnected around the engine. Normally these are the exhaust, top radiator hose, throttle/choke linkage, air cleaner, heater hoses etc etc. When jacking up, keep a check on the engine in case something has not been disconnected or is fouling. Make sure the fan blades do not touch the radiator core. Having jacked up the gearbox:
5. Remove the ring of nuts around the bell housing leaving one near the top.
6. Support the gearbox whilst removing the last nut, and remove the box taking care not to let the
box hang on the clutch splines.
Replacement of the gearbox is basically a reversal of these operations. If the clutch has been removed (which is a wise move), ensure that the plate has been centred using a dummy shaft or old constant mesh pinion. Coat the splines lightly with white grease (sometimes called "backing plate" or "expander" lubricant]. Take care not to allow the gearbox to hang on the clutch splines, alignment of which may be eased if the gearbox is in gear. Do not forget to fill the gearbox with oil, allowing time for oil to work through to the freewheel.”
I had done this operation on Rover 10s (1946-7) (too) many times. For the bell housing to get out it is necessary to remove the lower part of the fire wall. Use two jacks - one to support the engine and the other (on wheels) to support the gearbox – so that the gearbox is not hanging on the clutch housing studs or the clutch itself. Otherwise it is very difficult to pull it out.
See also here:
http://lulisml.wordpress.com/2013/07/03/clutch-woes-6/
You can also see here a picture of the car without the front floor and lower fire wall – the gearbox is exposed and available for removal:
http://lulisml.files.wordpress.com/2012/02/lifnei.jpg