Head is 12G940 casting number. Commonly used number on a variety of 1275 heads here, from Cooper S MK 2, Clubman GT, Morris 1100S (1275), to early 1275 Moke.
12G1505 crank is large crankpin journal, was used in late Clubman GT?, late Morris 1100S manual or automatic, Morris 1300 automatic, Clubman LS, or 1275 Moke.
That engine number has been restamped but not by factory.
The rivet hole should be to the left of the 12.
Edit
Where is the crack you mentioned?
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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.
