last year i went thru the same problem. but i lucked out bill heard had bought a bankrupt dealers parts inventory, and the shipment just happened to have the idler arms . i got them at below wholesale and it still wasn't cheap. yes they are nla from gm warehouses. a local alignment shop had told me they could refurb my old arms and that wasn't cheap. my problem was getting the correct part number. i had a friend that looked them up for me and then i had a chance of finding the items. look at the micro fish and make sure the parts match up to the item, as i remember the part nos and parts were not listed correctly.
2007 chevrolet 2500 duramax 6.6
allison 6 speed
2004 classic 28 WB , Pro Pride P-3 hitch
centramatics wheel ballancers 300-556