Original Onans in 982, 1912
 

Does anyone know if they ever put the P220G in at the factory on these tractors, or was it always the older B48G engine?

I've never seen documentation on anything other than the B48G from the factory in the 982/1912/1914.

Very early 2072s had Onans in them, but I don't know if they are B48G or P220s. I wouldn't be shocked if they were P220s. They are pretty rare tractors, though.

I'm pretty sure my 1987 catalog lists the 2072 as having an Onan. I can check to see if it says which one.

The 2072 was built from 1987 to 1989 and the early ones did have the B48G's in them. I don't think the P series came out until 90 or 91 and by then Cub switched to Kohler. So your answer would be that the P series was a replacement engine. Can you take a pic of the engine tag or post the serial number of the engine?