btw, where did you find the pickups?
The pickups came from Ebay. I'm on several Facebook marketplace pages for bass gear, and I was looking up used Thunderbirds. The pickups came up, so I messaged the seller asking for dimensions etc. I then spotted the same pickups on Ebay (for less!) so I bought them from there.
Oddly enough I was reading about John Entwistle's Fenderbirds last night, and apparently Peter Cook recessed the pickup mounting screws. I did the exact same mod to these pickups before fitting them, and before reading the article.
I just bought some sort of Line 6 space station from a guy at work, so I will record clips using that in the near future.