I have the above crank shaft and wondering if it is OK to put in a MK2 Cooper S block and if so is there anything I need to know!

It's a big journal A+ crank,
1. your S rods won't fit unless you grind crankpins down from 1.750" to 1.625". And then machine the rods narrower.
Alternatively, fit a set of A+ rods.
2. the standard 1275 thrust washers will be .032" loose, you will need to use +.030" ones and probably surface grind them to fit. Because a Cooper S block centre main web is 1/32" narrower than all other 1275 blocks.
[edit] I have the opposite problem, an S crank in an 1100S block. I have to grind standard washers down.

[edit 2] you can still buy EN40B S cranks new but they are not cheap...
http://minispares.com/product/Classic/C-AEG479.aspx

Some people find a good S/H early Morris 1100S small journal crank, they fit straight into an S block with thicker thrust washers same as I said above.

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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.