Eerrrr.... my bad, I should pay better attention, im a bit stressed over the issue. Anything else I need to look out for?

The only other difference has to do with the lower intake. The 96-97 engines have a temperature sensor located in the lower intake near the thermostat while the 98+ do not have the machining for this sensor. This sensor on the 96-97 motors is for the PCM. The 98+ combine the PCM sensor with the gauge sending unit sensor located in the driver side cylinder head.

They should have swapped over the lower intake, but they could have drilled/tapped the hole out for the sensor. It too is NPT thread. I believe it is 1/2" though, but could be 3/4".

Im geting very agrivated, im being told that its lifters now, by somene else. How the heck can you tell the difference? Im trust my other Machanic over this one I think. But im still going crazy.

Does it sound like a heavy knock or more of a tick or tap?

I found an '05 4.3 from a truck for $900. It had 42000 miles on it. I put it in an '01 4x4 Blazer. It seems demand for the 4.3 is up with the boat people. Depending what has been damaged, you will have 600-800 in a rebuild. At least that what I added up on my old one. U Pull It may have something that can work for you. Good luck

Not sure I would call it heavy, it could be worse, but its def. Not a tap, a knock for sure, itsworse then it was just a couple weeks ago.

How is the oil pressure? I forgot to ask that.

I was going to get a new sensor this weekend, and then an oil pump if it still read bad, I didn't check it before the oil change, bit a few days ago I did an oil change with 10w-40 and I know after hat I noticed it was low,I assume it was low beforehand as well. It read almost 0 at idol, but when driving or revving its 40, according to the gauge... what are the odds its a lifter or somehig? Could I just replace the oil pump ( if its the pump and not just a sensor) and then run straight 40 oil with some lucas (say 4quarts pool and 1 quart of lucas motor treatment)? That's better then an engine swap and about a $40-$50 fix.

if that is correct on pressure, sounds like the lower end. Rod and main bearings.
i have had bad experience with lucas and 10w40 on newer GM engines. 5w30 without anything is a general rule. i would get an accurate read on oil pressure to verify.
is there any metal in the filter or on plug magnet?

is it a 4wd? if it is the front axle is in the way to drop the oil pan.

Its 2wd