Stu
Ok, "
gauge sender" -- THAT clarifies that part.
But sorry I must be dense. Or CRS. I put your post aside to see your pics and am still mis understanding what you claim about a "tractor" pressure sender (and what it has to do with a C-30 vs a C-34.)
I know of no other oil port on the D850 or D950 block. Port or starboard or front or back, on a "tractor" engine or on a Kb genset engine. See the tractor (pic #1) and genset (pic #2) oil ports below. Same port that I explained to Matt in my post below.


There's no pressure gauge on a Kb tractor, at least that I have heard of. (
Admittedly) I haven't seen all
Kb tractor parts manuals, but the half dozen or so that I have shows no pressure gauge -- and I have seen no (tractor)
engine manual that has an oil pressure sender.
The only "other" oil port (and that was on an M-25, not the XP, and not on tractors) is what I described to Matt. And the remains of it is in your photos. The bronze (signifying Universal, not Kb tractor) hose leading from the oil port was OEM on M-25s. The machined block was OEM on the M25s. Universal unscrewing the oil switch and installing the hose and NPT/JIS threaded block was part of its "marineizing" the Kb D-850 block. See parts #11 and #20 below (in M-25 manual not Kb tractor manual.)

At some year (unbeknownst to me) Universal discontinued the system (but that's unrelated to a C-30 or a C-34 or a Catalina vs another manufacturer.) Certainly, engines with a 3" Hx DO NOT have that block. Saying that he had the remnant of a hanging hose, led me to believe it may be the "oil hose." If I can see some pics, I might be of more help on that.
Regardless, on the C-34 vs C-30 comparison, if one can get at and switch out the Hx on a C-34, one can get at that OEM M-25 oil switch location -- it was on the SAME bracket (until Universal "moved it back" to the engine block.) Although I know so little about how C-34 and C-30 engine installations differ, I BET right now Matt wishes he had the OEM M-25 oil block that I described (that you say won't work on your boats) because he'd have the switch out and replaced by now.
Why we have a idiot light/buzzer is because the engine came from Japan with only an oil switch. It has nothing to do with Seaward/Bristol/CTY engineers, or removing something (for a C-34 install) that's on a tractor. And I'm not sure how describing the OEM hose is disparaging anyone. The reason we don't have a pressure sender and gauge comes down to two things 1) Universal didn't provide that option at that point in time (it did later), and 2) the chief Bean Counter didn't pay to add one. It has nothing to do with the panel designer. manufacturer, or installer. Fast forward - the shuttle blew up because not because of the designers, but the (political) bean counters who didn't
listen to the designers.
Bottom line - I felt an oil gauge was worthwhile to add, and it can be done on the C-34 also. Not quite as easy as 1-2-3, but doable -- I did that this season on three M-25s/XPs.
kk