Can't help you on the filter sandwich plate.
The banjo bolt thread in the block though is 5/8-18 UNF.
Karcraft sells the proper fitting to go to 1/2 BSP oil hose (Cooper S etc).
Or, you can make them from a brass 1/2BSP x 3/8BSP brass nipple (Bunnings sell them cheap)= just machine the 3/8BSP end down to 0.625" diameter and run a 5/8 UNF die nut down it in a lathe.

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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.
