I never saw any mention of the transmission except for the clutch and flywheel adapter. Granted, I didn't sit through the entire thing, but skipped scene to scene. If it was never mentioned, there's no guarantee one way or the other that the trans is still stock. Since everything was painted silver, even the front mount (*oh my*), that tells me the trans was out at one point.
Even still, a stock trans can handle quite a bit - Fuzz can attest to that. But if they're going to be drag racing it, yes, first gear will be the first to go... unless they are launching from second.