91chevy

i have a 1991 chevy k1500 350 engine, 4x4. it has 225k miles.
ok so i have a couple problems i havnt been able to fix i have put new oil, and filter, plugs and wires, fuel filter, and rebuilt the throttle body/fuel pressure regulator.
i have taken it to a shop and the fuel pressure is good. next i want to take it to someone and not let them give it back till they tell me how i can fix it but worried it will be too exspensive.
my truck has a bit of a hard start on a good day takes 5+ seconds of cranking to get it started on an average day, if i park the truck on a hill it will start fine but idle low and die about 3 seconds later, if i try and gas it its boggy and doesnt want to raise rpms but once they are up then it runs fine.
next the oil pressure is in the red when idleing while in drive slightly about it when in park or driving. it used to seem like it was rpm dependant on the pressure but now as i drive the oil pressure visibly goes up and down, even at full acceleration the oil pressure sometimes stays close to the red.
i am not very savy on lingo but if you wouldnt mind giving me the name of whatever it is i can research what i dont know what it is.
thank you for any and all help!

sledge.impy

225k miles is quite a few.

What weight oil are you running now? You probably need some thicker oil in there.
Have you replaced your oil pressure sensor?

91chevy

i took it to a mechanic they replaced an oil pressure switch, but now after running it for a while i turn it of to go into say walmart for 15 mins come out and it will start and die in about 2 seconds then i have a really hard time getting it started again, i can let it turn over for 30 seconds and it wont even fire so its a fuel problem to me but i have no idea for solutions. the motor also only has about 60k on it.