As part of this winter's projects, I'm replacing the injectors, glow plugs and other parts of my Universal M-35A(C).  For years I've looked for my Universal's companion Kubota parts diagrams/list.  I just cracked that nut.  I'm sure I'm not the first, but I thought I'd pass along what I learned, for those still wielding their nut crackers.  At the end of this topic, I'll show the $avings I realized.

Summary.  Kubota's engine parts lists are available at https://apps.kubotausa.com/illustrated-parts/.  But, you can't just enter engine model information.  A Kubota engine parts list is just one section of a Kubota machine parts list.  So, you have to know what machine used your engine.  Here's the basic work flow:

    Universal Engine Model > Kubota Engine Model > Kubota Machine Model >  Engine Parts Diagrams & Lists

Attachment.  The attachment is a zip file with the cross references I will describe below.

Universal Engine to Kubota Engine Cross References
Our forum and the whole wide web is scattered with information.  I have attached two cross reference sources that I found helpful, at least in my search. 

1. History of the Universal Diesel Motor.  I extracted this text from downeasternyachts.com.  The source is at the end of the text.  I'm not sure when it was created.  It has information through at least 1999.
2. Universal Diesel Engine Data.  This is the creation of a company that, so far as I researched, no longer exists.  It states that it was last revised 8/10/2005.  I didn't keep track of where I found it.  My apologies to that source.

The two references, where they overlap, match up, except for Universal Models M3-20, M-25, and M25XP.  Universal Diesel Engine Data appears to incorrectly identify the Kubota Models as beginning "Z-***" rather than "D-***."

Kubota Engine to Kubota Machine References.

1. Kubota Machine to Engine Cross Reference.  I didn't keep track of the source for this reference.  Again, my apologies to that source.  I found this list to be pretty exhaustive, though it was missing some information that I found in the next reference.  I don't know how to read the full engine model identifications, so I don't know the importance those distinctions carry.  You're on your own here.
2. Kubota Tractor Model to Engine Model Cross Reference.  This is a big file, but it's a searchable .pdf.  I found that it is sometimes less specific with its engine model identifications.

Combined Cross Reference Table.
This is my creation--so use it with great caution!  I have tried to accurately pull together information from the above references.  Use it as a data source, not an authoritative reference!  Go back to the original references to verify my information.

Savings.
Getting to Kubota parts numbers gives you access, of course, to Kubota OEM parts, but you also gain access to non-OEM parts.  For example, the Kubota diesel specialist I went to (not a dealership--they wouldn't work with me, but kindly directed me to the specialist) recognized my injectors as manufactured by Denso.  I got OEM replacements from him for $72.00 each, compared to Universal's $349.70 each.  But, non-OEM replacements are available from Walmart for about $30 each, and I found a set of 4 injectors on Amazon for about $60!

Here were my savings: