Check your head studs to ensure the nuts have not run down and bottomed on the threads. This is more common than you think. It is common to need to double up the washers with ARP studs. Personally I would pull the studs and try a session with the stock head bolts and see if that cures the leak.

Cheers, Charlie
If It ain't broke, Modify it!
87 Montero turbo Converted back in Spring1989
95 Montero SR 3.8 DOHC Only one?
93 Pajero 3 door 6G75 Mivec with paddle shifted 5 speed
Then a Gen2 SR with full coil independent suspension.