The 71 C-body idler will bolt to an E or B body to match a fast ratio pitman.

The fast ratio pitman has a smaller taper on the end ball joint than a C-body pitman. So it won't bolt to your factory centerlink. They also have a large output shaft diameter that all 73-up power steering boxes in A/B/C/E/F/M/J bodies have.

The C-body pitman has different spline indexing keyways. So if you bolt it to your B/E body the steering won't turn all the way to one side but turn too much to the other side. About 20 years ago I talked to a guy that bought what he thought was a Fast Ratio pitman the car wouldn't turn all the way to one side. And it rubbed stuff. A mess. I'm guessing it was just a repackaged C-body pitman. It was bought from...wait for it.... Barracuda Classics!

I'm not sure if the C-body pitman is the same geometry at the Fast Ratio T/A pitman. But the repro Fast Ratio pitmans have "Fast Ratio" casted into them. So they are not just reworked C-body pitman casting.

The F/M/J pitmans are not long enough to be Fast Ratio. Nor have the correcty geometry.

So in conclusion, you need to get a Firm Feel Fast Ratio.