Although one can only read so much into these numbers but nevertheless, you have quite the full gambut of comparable engines above (and some more, though missing Landi engines).
The 2LT(E) and Nissan RD28T are the most likely candidates for CJ7 diesel conversions apart from the 1KZT. The 2LT(E) is the same price as the 1KZ but with economy ranging from 8-10km/l. The reliability of the 2LT(E) is a debatable subject but in my experience its not any worse than the 1KZT. The Nissan RD28T is a decent replacement option as it is considerably cheaper, though you would have to double check parts availability which is a major problem in the North but may be better in Karachi. Being a six cylinder it sounds great and is very smooth to drive, but its a tougher engine to fix if things go wrong. The 13BT and 5LE are relatively expensive engines (possibly PKR 150k+) though much more solid motors, not sure on consumption but can't be as bad as 1KZT and no better than 2LTE.
The CRDs look great on paper but practically speaking there is as yet no jugaar (that I know of) to mate them with our local diesel and ensure reliability. The KDs in D4Ds are notorious for pump and nozzle issues after 50,000kms which are very expensive to fix.
Having said all that, if you actually have the 1KZT in there and its running well, it probably makes little sense to replace it with anything for the sake of economy.