172 diesel help

My 861 diesel suddenly stopped running while I was mowing. Pulled it into the shop and after searching I found that it had a broken camshaft. sheared off right behind the timing gear. As I got deeper into it, here is what I found: Hydraulic pump gear is not damaged. The crankshaft gear has one broken tooth. The skirt on number 4 piston broke off at the lower oil control ring groove. the pieces were in the oil pan. There is no engine balancer and appears that it never had one (no gear on crank). Rod bearing on #4 is standard size. Don't know what others are since I haven't taken them apart yet. My questions for the experts are can I replace the cam and piston/rings in #4 without doing a complete ring - bearing job. I am going to plastigage the crank to see if it is still in tolerance. It had excellent oil pressure at 40 - 45 psi and started easily even cold.

Here's my experience and opinion:
My 1801 industrial TLB has a 172 diesel. When I pulled the pan it had a piston with skirt broken. after removing all the pistons the others were cracked. I had other used pistons that had cracked skirts so I took 4 pistons with cracked skirts to a friend and had the skirts welded, filling in the lower oil ring land and installed the pistons without the rings in the lower grove at the bottom of the piston. This was 12 or more years ago and it is still running and performing well without oil consumption or any other ill effect.
My justification was that the 192 diesel did not use pistons with that ring, 8N started with a 4-ring piston and replaced it with a 3-ring piston, and few other diesel engines(except 2 cycle) use a ring at the bottom of the piston. Also the ring grove at the bottom of the skirt weakens the piston. Most of the pistons removed from the 172 diesel will have cracked or broken skirts. My engine starts great, runs great, and runs clean. The last 172 Diesel engine I built for a friend, I left the lower rings off the bottom of the skirt, and it worked out great.
I would pull all the pistons and check for cracks, weld any with cracks and even weld the replacement piston to prevent cracks and breaks in the future, then install them without the bottom oil ring. I have been working on these tractors and engines for a bunch of years.

Interesting. Ford had another problem too and that was cracked heads on their 4 cyl engines. Company over in E. TX. is a Ford parts dealer and reman facility. I was over there years ago and walked through their shop. Very interesting how they repaired the cracked heads. One of their specialties was a drop in gear shift tranny replacement for an SOS at $1750 which I thought was a super price at the time since you got a rebuilt tranny and all the hookup necessities. I happened to have a 4000 4 cyl SOS at the time and this did catch my eye. But my SOS was still functioning suitable enough and I didn't need it......actually I couldn't afford it at the time even if I needed it.