Alloy bells are extremely unusual. Are you sure it's not for an OHC motor or SBF? None were made here AFAIK for the whole duration of crossflow manufacture.
BW34, 40, C4 - all cast iron bellhousings.
Some early 3.03s were shipped from the US with cast alloy bells but that was over by 1967; these are rare but use a dedicated clutch setup and sandwich plate so are not generally sought. I am chasing one simply to spec out and then dump.
As to manual housings - if by "left side" you mean when viewed from the rear of the car looking forward, it is either a Cortina unit or post-catalyst "XF" series. Some have humped backs that may accommodate a twin-plate clutch.
Check your starter mesh; should be fine but not worth putting off until after installing.
If you can post pictures, it would help too.
