If you already have them both, use the bbp disc's and 8.25 from the Dart and put them in the Scamp. Hell, you can swap the whole driveline over, since it runs already.
Or as Al said, sell them both and buy one that suits you better.
Second the vote for moving the drivetrain and brakes to the 71…my opinion is simply based on my dislike of the beak front on the 73+ cars…maybe transplant the front from the 71 to the 75 and part out the rest?