Technically, those are not 340 rocker arms and shafts. They will fit on a 340, but are not 340 adjustable rocker arms - they only made approximately 5,200 340's stock with adjustable rocker arms - 70 AAR Cuda and 70 Challenger T/A and those are different from these.
Those are 273 adjustable rocker arms.
I would recommend making a new for sale ad with them listed as 273 adjustable rocker arms. There is a market for these and people will buy them, if they know what you have. However may not look with them listed as 340 rocker arms. They will just read the title and move on without opening it, thinking that they are the standard non-adjustable 340 rocker arms - which are a "dime-a-dozen" standard small block rocker arms. I think you will get more interest in them that way.
Make sure that you put "273 adjustable" in the title and description so people know what they are. The photos also help with the sale.
