Large sector steering boxes didn't come out til 1973-74....
And I don't think anyone makes a large spline pitman arm to fit the older A bodies...(72 and older)...without changing all the linkage
Never have heard of a 'big block' pitman arm.
Large sector steering boxes were out long before 73, but not in small block a-bodies. My old 69 Polara wagon had one (the only car I've had with one from the factory that I knew of). As for the big block pitman arm, why don't you go look at the old parts books................
