Originally the pipe points more-or-less straight back to the hose, which is secured to a bracket welded to the side of the battery box, and the hose attaches to the top of the 3-way union on the axle, this from my 75 V8:
But for UK 77 and later at least the bracket changed to one bolted to a welded nut on the rear of the battery box, and the pipe now connects to the hose pointing downwards. Also the hose now attaches to the off-side of the union on the axle, and the off-side pipe comes off the top. This is probably because the union had to move closer to the diff because of the ARB brackets. Image from Charles9 UK on the MG Enthusiasts BBS.
The Leyland Parts Catalogue shows the hose as having 'gasket' 233220 to the union on the axle, which the catalogue drawings show as having a notched edge, but all the suppliers pictures I have seen show it as a plain copper washer.
3H2424 from Leacy at £7.50 - what would be the top port for the hose pre-77 definitely different to the other visible port.
BTB657 for Triumph models from Moss Europe at £17.10 - the two visible ports with the same recessed thread, although the mounting boss is in a significantly different position.
AJA5028 for the MGA from Brown & Gammons at £16.07 - possibly four ports although one could be blanked off, the lower right (in this image) port looking correct although the lower left is completely different.