Wow, the guru himself! Thanks Jerry. According to napa, they list identical sending units for the 86 diesel vs the 88 gas models, so there was no point in buying a new one from them. I swapped sending units yesterday and there's an improvement. I als replaced the filter a bit early in case it could have been bypassing and I refilled with rotella 15w-40 oil. It starts up at about 40 -50 psi. Once up to temp the pressure reads about half way across the 0-30 segment of the gague, an didn't drop any lower while running 3k rpm at about 65mph.
This still strikes me a somewhat low, but I know I've read here that this is fairly normal range for these motors. This one has 152k on the clock and was supposedly replaced by isuzu around 50k due to a "rod issue" (info from previous owner). Is there any concern that the bearings are loose with pressure readings like this?
I suppose the other thing to investigate is the turbo. The chilton manual I've got is worthless with respect to this. Anyone have good search terms for this forum regarding turbo specs & rebuilding?

Thanks again