WHOA WHOA WHOOOOOOAAAAAHHHH!!! Back up there big fella!!!
This is starting to sound like you are trying to use a 68 idler on a 67 K. The 67 idler should have a STUD mount and nut, and the 68 / later has a through bolt and nut
Somebody doing a conversion
https://dartslantsix.wordpress.com/2012/10/07/idler-arm-conversion-67-to-73/