IDLER ARM QUESTION

If the washers are thin and hardened then yes they should go in there. Check the hardness with a small file. If the file cannot leave a mark, then they are hardened.By installing them,chances are better that the spacer tube inside the idler will not damage the K-frame over time, and chances are better that the bolt will keep it's torque. You may have to spread the tabs a hair.
Some brands of arms are very tight after the initial install. Sometimes it seems they need a boot to break them loose. But if yours is still very tight after breaking it loose, the car will steer strangely until it breaks in.This, firstly, is very annoying and secondly can take an annoyingly long time.
I have not had this kind of trouble with Moogs or TRWs.But I have had to un-install off-brand junk, for this reason. Off-brand BJs too.