In my opinion because you have gone as far as you have the easiest option is to lift up the rear of the bellhousing close to the gearbox so that the rear of the gearbox clears the chassis cross member that it sits on, undo the bolts that hold it to the bellhousing and remove it backwards. The pinion shaft will probably come with it but if it doese'nt just pull it out separately.
As you have discovered, remove the centre panel in the bulkhead and the engine together with the bell housing will come up and out with some slant on it towards the back. Chances are the bellhousing will need some fettling in the clutch release mechanism if it hasn't been done for a while. May even need sleeving. Most do but may have been done already at that age. Put some easier to undo bolts in the bulkhead centre panel when you put it back together! good luck.
