I swapped my '71 Sweptline and my wife's '79 LRE from 727 to 518. Built adapters for both that bolted to the factory crossmember...not pretty but they've both done over 20,000 miles with no issues. If you've got the mount to go with the 518 and average fab skills it's not a big deal. You CAN do the "work of art" mount if you've got the skills and equipment. With the pressure and vacuum switch setup for shifting the OD and lockup, it's an awesome swap and well worth doing.