Need ideas on what might be the cause
 

Problems.
Truck ran. Started having a metallic rattle from engine so I parked pulled plugs took belts off and tried to turn crank by hand I get almost 350 then dead stop.
Took intake plenium off noticed oil/water residue on the gasket above #5 intake.
Ran a bore scope trou plug holes no obstruction or moisture pulgs looked normal.

Runner is a manual transmission

I am guessing it's the 3.0l. Else, no #5 plug.
Belts: did you take off the timing belt? (3.0 is not interference style, right?)
Take off valve covers and look if everything is moving like it should.

Took acc belts off and valves look good. I have not removed timing belt yet
i have 2 ideas on the issue first being from when piston rings were replaced the bolts holding the connecting rod to crank shaft came loose. 2 I know my input shaft bearing is worn so is the clutch possibly a failure there getting cought up. Yes it's a 3.0. And thank God it's non interfere

Pulled motor removed passenger side heads and found
https://cimg7.ibsrv.net/gimg/www.yot...d6688e1b61.jpg
Mechanical damage to piston cylinder wall looks goos
https://cimg1.ibsrv.net/gimg/www.yot...3c7f5bc69f.jpg
Mechanical damage to head
time to look at either grinding down the damage or replacing the head.. and swapping the piston out. Any tips on flushing out oil collent gallery to get what ever got cought in the cylinder out. Have not found anything that would have caused the damage yet

The object is most likely trapped in the catalytic converter now. The shape and size of the damage has me thinking it was a washer or sorts.

Cat was cut before I recirece the truck. I am hoping you are correct but I don't think I will get that lucky because as soon as I pulled the block I tredt turning the crank but it was still binding

Found a smashed nut seams to have been the issue. Any thoughts on if the head is repair-able or needs replaced