I don't know about Europe or the ME, but the 1.5F heads in the US are either 60050, 60051, or 60052: Each was used for about 3-4 months of production over the course of the year the F1.5 was installed in the FJ40. The 60050 and 60051 look identical, externally, to me.
The last few months of production, the 60052 head has the 'step-down' head-to-manifold-studs because it seems the mfg was gearing up tooling for the 2F head. The 60052 head has 12mm stud holes, but still had to accommodate the 10mm Int/Exh manifold holes, so the step-down was a quick bridge.
These head numbers are not in the EPC or Microfiche, or at least I've never been able to find them listed anywhere... @65swb45 told me most of it. The rest of it became clear after acquiring a few different '74 heads. Also, be aware, the 1.5F head uses Head Bolts specific to that engine only.
The last few months of production, the 60052 head has the 'step-down' head-to-manifold-studs because it seems the mfg was gearing up tooling for the 2F head. The 60052 head has 12mm stud holes, but still had to accommodate the 10mm Int/Exh manifold holes, so the step-down was a quick bridge.
These head numbers are not in the EPC or Microfiche, or at least I've never been able to find them listed anywhere... @65swb45 told me most of it. The rest of it became clear after acquiring a few different '74 heads. Also, be aware, the 1.5F head uses Head Bolts specific to that engine only.