Did you order idler arm for 68 w/big block application? I seem to remember seeing in parts catalog that there were different "special" parts but never saw a comparison, how much difference there was.
Forgive me if I'm wrong but I think the pitman and idler for pre 73 need to be a matched set, i.e. both for standard applications or BB application, In order to level the linkage.
The 73 idler arm absolutely will not work unless you change pitman arm and center link to 73 up design. Those have stud pointed down, zerk on top. No "special" parts required for this later design.
There is a slim chance that the previous owner also purchased the standard application arm, then heated and tweaked it to clear.
