2003 Dakota regular cab 6.5 bed please read description. possible repairs needed

The good news a solid no rust southern truck. Truck has the 3.9 V-6 engine. I just had a valve job done heads planed and valves ground all new gaskets. After doing all this i heard what i thought to be a knock or rattle that sounded like it was underneath d/s floor when i moved it. I am not sure if this was a lower engine knock or a loose cat or heat shield noise. I can not get it to make the noise again to diagnose it and i don't want to pull it apart or spend any more money on it to find out. I would not feel comfortable selling it without disclosing this. It may not be anything or may be something simple or major not sure. It also has a new radiator, ater pump and hoses. Would recommend tune up. The ignition parts look to be original. Tire are getting a little low on tread but seem to be worn evenly. I would recommend looking at vehicle in person or have someone inspect it for you. I took a picture of the gauges with it running so you can see there are no warning lights on at this time. Everything is working on truck and looks like it was repainted at some point. Some dings, aves, cratches but still looks decent. Interior has a few burn holes. Selling as is no warranty no returns. A non refundable deposit of $300.00 is due at end of auction. Remainder due within 7 days. Will work hauler if having shipped. I would not recommend driving long distance until it is checked out. Final payment can be cash in person, ayPal or Bank check but must clear before vehicle is picked up. I have a clean title in my name.