The M-25 is built on the Kubota D850 block, the M-25XP and XPA on the Kubota D950 block, and the M-35 and M-35A on the Kubota V-1200 block. All those Kubota blocks and the Universal engines use the SAME coolant circulation pump. So the P/Ns for either Kubota engine block will fit the other. However, you may locate different P/Ns for the same pump because Kubota keys its P/Ns to the specific application in which the engine is used (e.g., B6200 tractor, B7200 tractor, Bobcat, excavators) and not keyed to the engines themselves (D850, D950, V1200) So there are oftentimes different Kubota P/Ns for exactly the same physical part (like the coolant pump.)
Additionally, Kubota is constantly updating and assigning new P/Ns, so the current P/N for a coolant pump today could be a different P/N tomorrow. So the pump P/Ns in the Kubota parts manuals on the wiki page Wiki Parts Manuals are the original P/Ns, and they have changed over the years.
Luckily, there is a good source for updated P/Ns - www.messicks.com (an agricultural Kubota dealer that also sells online.) Messicks isn't the least expensive on OEM Kubota parts, but it is a very knowledgeable source, the parts folks are super cooperative and helpful, and Messicks provided many of the Kubota parts manuals that are posted in the wiki.
Kumar Brothers (www.kumarbrosusa.com) sells many (but not all) aftermarket parts for our engines. There are other both OEM and aftermarket Kubota parts sources, such as Country Sales and Service -- so do your homework before buying.
The current (7/2019) P/N for the coolant pumps are below. If you plug any Kubota P/N into the Messicks site:
from westerbeke online or your local dealer: Westerbeke.com online parts P/N 300203 (OEM Universal Motors part) $385.30 Mounting gasket P/N 300204
From Kubota dealers, KumarBros, etc, use the Kubota P/Ns:
Old P/N: 15534-73030 Current (7/2019) P/N: 15534-73033