I do agree with you leathermang.
It is always best to put things proper & right. If it was one of my machines that I make a living from I would be doing a rebuild.
Mark appears to want to get the car going reliably for as little $$ as possible. He doesnt appear to be wanting to do a full restoration or rebuild. That is why I have suggested that he may be lucky & get by with a hone / second hand piston / rings. He may be able to do that for under $200 in parts if he only rings that cylinder.
Heck its number 3, I suspect you could do it with out removing the motor from the car.
There is always a risk associated with that. He probably should inspect all 5 pistons out of the motor. I cant recall if he did a compression / leak down test. If the motor goes back together & runs ok, its a win !!

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving