955L cat loader motor issues (grey market at that serial)

we have a 955L we just purchased an it has had an awful knocking in the motor,,, pulled it out an was guessing for bad crank an a rod or two ,,, needless to say pulled the head off an the number 4 piston has been busted an the top all beat up due to it dropped both valves into it,, pulled the bottom apart to find the cranks in perfect shape an all rods are fine,,,, needless to say the motor serial number tag on block matches the same serial number to the tractor 31J773 called cat an talk to my friend an he looked it up an the tractor is grey market an from Japan. so I went to my after market parts guys that I get all my motor kits from an gave em the part numbers off the main ,rod bearings an piston numbers an cant any one get the parts,,,there good numbers but the availability is from Japan,,, so I called my cat dealor back an gave em the piston number an he looked it up an said he had a piston sitting in a warehouse up north but couldn't do anything with bearing numbers,,, me an my cat guy have allways dug threw cat sis till we found an American serial number tractor close enuff to use to go by to order our parts buy, but were having issues with this motor unlike we have before... this motor I noticed when I removed the bottom end I found that the main an rod bolts all had cotter pins threw em to hold the nuts from backing off,,, never seen that before.. also the motor is old enuff for it to have a canister oil filter an not a spin on. not sure what were gonna do ,,, not sure if we find a lil newer motor if we can adapt all our exhaust an intake manifolds too,,, I know on a few 955L s ive worked on before they had the big square injector pumps an differ style belt tensioner,an they have the big heavy intake manifolds. any idea guys what to do ,,, just scared if we went with an whole completely newer motor with out changing an putting my older stuff on newer block that my hood would fit properly or would have to modify with cutting hood up... don't wanta look shady.

955L cat loader motor issues (grey market at that serial)