If you are wanting to add power steering to your 1970 Mustang, there are some issues regarding the centerlink and tie rod parts that you need to be aware of.

There are differences in the sizes of the studs in the ends of the tie rods and the mounting holes for the ends in the centerlinks between 1969 and 1970. Interchangeability is not cut and dried. In 1969, generally both mustangs and cougars used tie rods and centerlinks with smaller studs and mounting holes. In 1969, the Boss Mustang and Cougar Eliminator used tie rods with larger studs in the ends and centerlinks with larger mounting holes. In 1970, this carried over so that all mustangs and cougars used the larger tie rod studs and centerlink mounting holes. This also pertains to the holes for the tie rod ends on the spindles used in these cars. This also means that the centerlink bar diameters are different. The regular 1969 bars are smaller than the 69 Boss/Eliminator and all 70 Mustang bars.
To sum up:

- Smaller sizes for 1969 Mustang and Cougar (except Boss and Eliminator)

- Larger sizes for 1969 Boss and Eliminator and ALL 1970 Mustangs and Cougars.

This information is verifed through the Ford Master Parts Catalog, research on Cougars through a Ford Dealership parts department, and by others who unfortunately have tried to install the centerlinks with the smaller holes on their 1970 Mustangs. The tie rods won't fit. So if you want to add power steering to your 70 Mustang, you must use a (D0ZZ-3304-B) 70 Mustang only center link (or a 69 Boss or Eliminator). The 70 Mustang centerlinks measure 23 1/2 inches from the stud for the idler arm to the hole at the end. Contrary to some opinions, there is no distinction between big block and small block engines. The engine size does not matter pertaining to these parts. The idler arm should be a power steering version 67 to 70 Mustang. The pitman arm, connecting the draglink control valve to the steering gear box, should be the power steering version for the 67 to 70 Mustang with the 1 1/8 inch sector shaft. You will know a power steering pitman arm because it has holes on both ends. I recommend just getting a new or rebuilt control valve and power cylinder.

Hopefully this information will keep anyone from acquiring incorrect parts and then finding out at installation that things won't fit.