New wheels , Wrong lugs

I have a 1966 Barracuda. Due to disk brake change on the front my cragar wheels took a conical lug nut. However. on the back I am still 5x4 with cragar wheel that take a shank lug with a washer. The fronts went on very well. But, the lugs on the back would tighten up and leave the wheel loose. Had to mill off the end of each shank nut to get them to tight the wheel. Yes I did talk to cragar and they were no help.