Jesper,
That stroker is going to like the added duration of the 425 intake - no inbetweens on that . Depending on the head, it might not need anymore cam than that anyway. Just hard to say.
Difficult thinking a reply like this all the way through being where you live but, depending on finances , quickest lowest cost way vs selling the cams and starting new try the 425-378. Set both cam centerlines high for starters . Bring the intake down if launch needs managed. It might be tough bettering your 1/8 mile times you already have because it's the 1/8.
I have a question - does it cost less for you to buy a set of WebCams because of not having to ship in the cam cores ? have you checked Megacycle , Kent in the UK and the Tornado Racing cams from GroBewachter?
Got a pic of your bike so to get a better idea what you have and anything about the clutch, wheelbase, fuel system and exhaust system you want to tell about?