On mine the holes in the front and end of the oil gallery were BSPP (parallel) threads. BSP (tapered) fittings wouldn't screw in far I found. I had to source BSPP fittings and use fibre washers under them. I also use Loctite pipe thread sealer which comes in a sort of gluestick type package. I try to avoid the PTFE tape in case any of it strips off and clogs the oil ways.
Simon
Simon