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I wanted to know if the 1969-1979 Mustang fastbacks had the same chassis as the 1971-1973 mustang fastback?

Which leads me to my other question. If they are or are not the same chassis can the parts still be swapped between each other?

For ex. If there is a rack and pinion setup for a 1969-1970 mustang can that be used on the 1971-1973?

Both seem to have the big body chassis setup but different shape bodies on top.
 

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I wanted to know if the 1969-1979 Mustang fastbacks had the same chassis as the 1971-1973 mustang fastback?
No, completely different, the 71-73 was a complete departure from the 65-70 cars.


Which leads me to my other question. If they are or are not the same chassis can the parts still be swapped between each other?
No, it would be like trying to use Toyota parts on a Ford.

For ex. If there is a rack and pinion setup for a 1969-1970 mustang can that be used on the 1971-1973?
No

Both seem to have the big body chassis setup but different shape bodies on top.
Your eyes are fooling you. The 69-70 is closer to the 65-68 cars, the 71-73 is larger, on its own platform, and stands alone.
 

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No, completely different, the 71-73 was a complete departure from the 65-70 cars.
That's an exaggeration. They're still very similar in design, on the same wheelbase, carry many of the same basic mechanical/powertrain parts, and the brakes and some suspension parts will interchange. They are as big a departure from the '70 cars as the '67s were from the '65-66 (or the '66 Falcon/Fairlane was from the earlier platforms.)

But the shell is wider, the rear axle is wider, they are quite different in detail.

The '71-73 car had one critical improvement: it got a GM Saginaw 700-series steering box. This finally got the car's steering on a par with, say, pretty much every GM product from the early '60s onward that used that same box design.

There's not much reason to think about a rack and pinion on the later cars. The 700 box is excellent, nothing like the linkage-boosted garbage Ford used on the earlier Falcon-chassis cars (and even later ones like the Granada/Monarch/Versailles) and can be tuned for just about any level of assist or anything else you'd want.

There might even be 670-series boxes that'll fit, I'm not sure - the 670-series is the latest Saginaw box with a lighter case and even better valving. These are a common retrofit in the GM F-body world.
 

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Fatman Fabrications now has a suspension kit for 71-73 that includes a rack and pinion.

I had the steering box rebuilt and had an alignment done on my origional setup and it
is pretty good now. It really tightened up the steering and doesn't wander anymore. As JEM said, it's a good setup. It's still not quite as crisp as a new R & P car but it's pretty good and was a lot cheeper to rebuild the box and align.
If you want new car handling, looks like the Fatman setup is the way to go.
 

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Fatman Fabrications now has a suspension kit for 71-73 that includes a rack and pinion.

I had the steering box rebuilt and had an alignment done on my origional setup and it
is pretty good now. It really tightened up the steering and doesn't wander anymore.
Did you send it to Tom Lee at Lee Manufacturing (http://www.lee-powersteering.com) and have a 35oz spool valve put in it? A 14:1 straight-ratio box with a 33-35oz spool valve (IIRC the old WS6 Trans-Ams that ran that steering box used a 35oz valve) ought to be 90% as good as any rack out there, without the durability, header-clearance, and loss of steering lock problems that Mustang rack kits experience.

What alignment settings are you running? As much caster as you can get, 1/2-1 degree negative camber, around 1/8in toe (maybe less if you've got nice snug new parts) and have you done anything with the upper control arms?

The Fatman setup involves a certain amount more work and I wouldn't automatically assume that just because it's aftermarket it's superior.
 
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