Don't know about the timing curve, but the Speedmasters do have a higher rev limit. I've e-mailed Jojje asking him to post to this thread. It'd be nice to have his knowledge archived here. Also, I think he charges something like $200 to modify the rev limiter.
You're right about black boxes costing an arm and a leg from the dealer. I've never seen one on ebay and I look there on a regular basis. I think your best bet is still to seek out the Wizard of Sweden.
