Ppacker,
Yes, the serial number is visible and I think gives us a necessary clue to it's origin.
The use of 2 different size/style stamps would suggest this is probably a replacement engine (they came without stamped numbers) and the shop/installer or some other entity stamped this number to identify the engine.
When you get around to it (if you choose to) add a picture of the date casting codes behind the starter and we can give at least a bit more definitive answer to your question.
For answers on your other topics (transmission w/pto and front/rear axles), post new questions in the
Driveline forum for each as it's easier to respond to them separately to avoid any confusion on topics.
Dan
