The GT is a timeless work of design. There will always be subtle comparisons. What sets the 296 GTB very distinctly apart is the wrap around windshield.
You can buy the cap with filter cage made for a BMW for under 30.00 dollars (prices may have gone up). It does have the China stamp however. There are posts on this subject. I do all the maintenance on my GT for lapses mentioned above.
I am aligned with you on taking all the belly pans off to clean and inspect all underneath. Most important as someone mentioned before is to check the state of the oil pump belt ( if it has not been changed).
I have been using the FGT voltage surge suppressor kit for some time. I went on a trip once and left the key in the on position for 3 days. Knock on wood no issues yet.
Do you have a transmission cooler? Not related to your post but might consider one. I live in hot South Florida and fastparts adjusted mine with their tune. After driving never had them stay on. Mine stays below 210.
That’s the same unit I have....it has a few settings....I have mine set so that it does not pulsate every time I hit the brakes during heavy traffic. There is an interval setting so it does not become annoying.