Dullahan

I'm having issues with my new XJ I just bought. After starting my engine I have a a nice low knocking sound from the bell housing/flex plate area. Typical sound like a low end knock. At start up a grind, or clank sound is present as well. This will only do it at idle. I climbed under the Jeep with a stethoscope and with a positive confirmation by four other people, the knock/clank is coming from the slit where the inspection plate sits. Oil pan is quiet. I've also been to about four mechanics and they just keep telling me that my engine is shot and needs to be replaced. I have 166k miles on it. The oil pressure is not the greatest though and I think thats why they are pushing the engine issue. All four have not even got under the Jeep after what I told them and they just give it the ole ear listen. I had the oil pressure read with a mechanical gauge and it was at around 10 +/- a couple at hot idle and upwards near 40 at higher revs. I'm thinking my pump is a bit weak and the prior owner has 20w50 syn in it so maybe it's straining it as well? I will switch this out to 10w30. I tried to take the plate off and see if I could just tighten the bolts on the plate but they will not budge and I don't have an impact. I am planning on either taking it in and directly asking them to tighten the bolts if needed or just handing them a flex plate and tell them to replace it. I will wait a bit on the oil pump since I spent all my cash on this Jeep lol. I would love any advice or extra thoughts on this!