What about the return where would that go to?
The one coming off of the block just above the filter housing may be AN type. That is where my feed line comes from.
Someone had posted they (filter housing threads)were a British thread similar to npt, Ivle also read they are a straight (no taper) thread.
I have my oil temp gauge and pressure switch for my lift pump in the lfilter housing and used npt bushings for both, so...
Yeah the HTT one is a BIOTCH. I had to remove my feed line because it would seep at one of the unions on the check valve.