'67 Dart with '68 idler arm?

Sorry about that. My thinking on this has changed since the first post. Where I'm at now is that I just want to replace the arm that I have with an identical arm so I'm just looking to identify what's on there which is why I posted the measurements. I'm assuming that whatever hardware was used came with the arm and the only reason the tab would have been drilled out would have been for the sake of that hardware.

So I've abandoned the idea of using a '67 arm and just need to figure out what's on the car now and replace that. Definitely not trying to go deeper into any modification than I need to. This is a driver and my only car so I'm also trying to avoid too much downtime while I have it disassembled. Thanks again for all the help.