I put an s&s 106 kit into my FLHT after 67,000 kms, here's some pics of the old parts using nothing but syn3 from new. Thought you might want a look. I've owned the Cadillac since new and have never thrashed it and it's been serviced by the book without fail.
I think that I will try something else.
? oil thread in disguise? number 372. Nothing new here sorry. Just saying!
P.s. Neale, when you rebuild the cadillac, use a better oil.