What does this tag mean?

[sgoeser]

I have a new M35A2 built between 1970-1971. The engine tag states LDT 465-1D 5-87. So I feel I have the last run of the Multfuel engines with a better head gaskets and pistons. Am I right? I have no knowledge why the engine has been replaced other then maybe the shop was slow and they needed something to do that week so they replace the engine. The truck has 26,875 miles in 940 hours. That would be frame mileage and time not engine. Correct? Have I done well? There is no body rust or dings. Even the seats look in good shape. It has been stores in a heated warehouse in Colorado for years. Oh yes, after new batteries were installed the engine started in seconds and ran very smooth.
Now my question is what does the tag in the door means. The numbers are "92320200351" 5-27-91. What is the tag telling me?
Thanks for your help.

 

[sgoeser]

I forgot to add the Part number is 12354301 with a serial no. 3982352. Built by White Engines.

 

[Black Ops]

The tag inside the door is a Modification Work Order tag for the installation of seat belts.

 

[sgoeser]

Thanks for the answer. I though it would have been for something really serous.