Donor drivetrain question

I have '68 Dart with /6. Have found a '75 Dart 4 door with good running 318 and
disc brakes. What problems do you see swapping the complete drivetrain into '68. I suppose the '75 is LBP so my rallye wheels would have to be replaced. Is $1800 too much to pay for this donor car?
Thanks in advance for advice.