Gavin the one with the castle head should be tight! The torque reading I'll pass on but must be tight as it holds the taper in the shock arm. Now the other nut should be tightened so you have about 2 thou of play between the solid shoulder and the trunnion (do not lock it up tight the suspension won't work). When you have this knock over the washer against the flats on the nut to stop it turning. It should be a thin locking washer next to the thick one.
My Minor:
A Clarendon Grey 1953 4 Door Series II.
MMOC - 66535