Another oil pressure issue

[ZKWBQD]

So here is the skinny. 04 Tahoe, 5.3. Has 297k on the clock. Recently replaced oil pressure sending unit(posted pic of what under the sending unit looks like, could not see screen, horrible placement for sending unit). Replaced pick up tube oring, new oil pump, timing components, all associated gaskets, timing cover, water pump, oil pan, timing cover seal. On start up in the morning, it holds 20psi. After oil warms up, at idle, 5PSI. 65 mph-38psi, all according to the dash gauge. Debating on running a pressure gauge(Equus brand). I have seen there is a plate that bolts on the oil pan, next to the oil filter. Has anyone installed one of these on their Tahoe? Also developed the lifter tick after last oil change. Trying to see why the oil pressure was low, l held the RPMs at 2000, heard a puff of air, and the tick started. Any pics of your set up is appreciated. Just trying to make this thing trustworthy again. Taking a 3 hour trip in October and want to have the extra room, wife’s Kia is too small.

Side note, I have a non Flex fuel, and got a code for a P0178 recently. Says it’s a flex fuel issue…‍. Thanks for the info in advance. Much appreciation.

It's not a clock, it's an odometer.