Hopefully someone else with more specific knowledge will check in… but a couple of your questions are within what [I think I] know:
*** I’m pretty sure that “the Book of Norman” has the data regarding the s/n and the JAL#. Sounds like your car is about a month older than our Mk1a (ours is October build according to some friendly folks on the forum here).
*** The “shorty” oil filter is an adapter screwed into the block in lieu of the leaky hoses and flimsy bracketry from the stock remote filter arrangement… not sure how popular it is today, but it was highly recommended to me in the 80s when we got our car.
*** There are many, many Tigers sporting a variety of non-original engines, so a different block in a 54 year old car might not be surprising.