For anybody that is interested; I have just fitted a set of ARP head studs to a supercharged 4K motor in a clubman.
The part nos. are....AM5.000-1LB stud
AMN12-1 nut
AMW750N washer
cost US$9.98 each set x8
They torque down to 60 ftlbs ( thats 12,015 psi !!! )..a little bit more than the standard 48 ftlbs...