11862 is not the original engine number. This should start with either R or T followed by 3 or 4 numbers. I did wonder whether it could have been T 1852 but the T series engine numbers didn't go as high as 1862.
I always thought that the cylinder heads with studs going downwards and nuts between the fins were on 500cc engines whereas the ones held on with bolts from above were 600cc engines. So I am interested in your comment Klaus on the need to check the bore size to be sure.
36 4G, 37 VH, 54 KH(A), 75 Healey 1000/4, 52/53 ex ISDT KHA (project).
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist once more - but not Machine Registrar.