Fast ratio pitman arm for small sector shaft

Yup. You are correct. Will have to dimple the headers somewhat. But it's worth it for getting fast ratio...
If they only made a rack and pinion kit for the A body. (Unisteer on my 69 Mustang is excellent!)

Yeah I tried the TTI shorties on my Duster, there really isn’t much clearance at that head pipe.

They used to make a Unisteer rack for the Mopars but the resulting steering geometry was terrible, I believe it was discontinued because of that.

A-bodies really aren’t good candidates for the fast ratio steering arms. You’d be better off with a Borgeson power steering box (14:1) to lower the ratio vs factory (16:1). The other option would be a steering quickener, although that would require modifying the steering column. The Hotchkis Challenger used a steering quickener for a final ratio of 12:1, same as the fast ratio arms.

Howe Racing 5225 Howe Steering Quickeners | Summit Racing