These are really nice, really quiet pickups. I have a set myself and just put a different pre on them and they are good stuff. Because I just ripped everything apart in my bass, I just wanted to throw what I know in here, if that's ok...
The preamp is not the same as the US. It's actually a lot easier to install on other basses than the US one would be. The wiring diagram is available here:
http://squierguitars.com/pdf/current...0V-Service.pdf
Also, the width of the pickups, I BELIEVE, is the same as the 4 string Mexi basses. I say that because I was able to fit a 4 string pickguard on my 5 string bass.
They actually measure 3-5/8" x 3/4" and are 1-1/2" across the centers of the screw tabs.
"I'm half tempted to buy them, but don't really need them at the moment" bump.