NO. They will not work. Look at the Firm Feel site for the longer pitmans/idlers A-body applications. Only Schumacher Tri-Y fits for A-body. Virtually every other A-body will not fit.
Even stock 340 exhaust manifolds with stock type head pipes will NOT fit.
That application list for A-bodies is all WRONG.
PST, do you have pictures of one of your fast ratio pitmans installed in an A-body???