Idler arm bearing conversion help

So I am in the middle of installing the idler arm bearing conversion on my 63. The problem I'm having is that the stud on the idler arm doesn't have a hole for the cotter pin. When I took it off the car it didn't have a castle nut on the center link side, just a regular nut. ***? :confused:

The stud on the idler arm has a slot running down it like on the front wheels. Do I need to get a washer with the tab on the inside to keep the nut from spinning? Can I drill a hole in the stud to accept a cotter pin? Do I need to do anything at all? HELP! :(

I've got everything installed, but when I turn the arm back and forth the nut moves.

I'm pretty sure this is not the original idler arm. I found receipts from the former owner and the idler arm and pitman arm were replaced about 12 years ago.

Thanks.

if you have enough thread left after installing the nut , i would try drilling a hole for a cotter pin. if not enough space , maybe try some loctite .

Yeah, there is enough space to drill a hole for the cotter pin, I just don't want to screw up the threads (a new idler arm is expensive!:eek:)

What's strange is that there was no cotter pin on it before and the nut stayed on. I don't get it.

that almost sounds like the setup that i have with the large encapsulated nuts the truth is that it is driving me nuts also ill try to send you pics of what i got timbuk