51MERC-CT:
Thank you for the very informative follow up answer. I'll try the horizontal postion. I found this old thread that gives lots of interesting info about oil pressure sending units, their differences and their orientation.
https://fordbarn.com/forum/showthrea...3209&showall=1
On Jan 1, I did install both oil pressure pressure switch and the fuel pump shut off
switch horizontally as shown and both worked fine. Used crows fit wrench with ratchet handle and extensions to tighten fittings to back of 8BA block.