The plot thickens. Lunderic, you said your engines are mechanical V10, but which version exactly? LE401 820hp, I suppose? I'm asking because in my V8 LE403, which are exactly the same that Butch has in his boat but with no remote oil filters, the filter base assembly seems exactly the same as yours, BUT without that sort of extension holding the senders. There are instead just two caps, on both sides of the base, as per attached photo. So, don't ask me why, but it appears that with the very last version of mechanical engines (which were the LE403), they moved all those bulbs elsewhere, thought I still couldn't find where exactly! Or it's a difference between V8/10/12, but I think that's less likely.