Not a tractor engine! The lineage is as follows:

The B230 is a reduced friction version of the B23, introduced in 1985. This was achieved by reducing the size of the crankshaft bearings. At some point in its life they were enlarged again, though not to the original diameter of the B23.

The B23 was an enlarged version of the B21.

The B21, introduced in 1976, was a new OHC head on the late version of the B20.

The B20, introduced in 1969, was a bored out B18. There are two major types of B20: Early, (69-73) with SAE threads in the block and a 6 bolt flywheel, and Late (74-75) with metric threads and an 8 bolt flywheel. (there are plenty of other differences, but these are the most obvious ones)

The B18 was introduced in 1962. A clean-sheet-of-paper design, it was state of the art for a pushrod engine when it was created. relatively lightweight, rugged (larger main bearings than some American V8s) and with a short stroke, it was far ahead of anything comparable from the US, Britain or Japan.

There were marine versions of the B18/B20, but as far as I know, it was never used to power farm equipment.