Can someone tell me if this carb is for a automatic or a manual or does it matter? Thanks

 

Not by the picture. The only differences between a 4100 set up for an automatic or a manual transmission are internal. There is an abbreviatedFord part number on the left front mounting ear (tab) in the format of '6Z F'. If you have one marked with that number, it's worth about $800 to a $1000 as it's a GT-350H carb.
Jim

 

Does it have the kickdown linkage for the automatic trans ?

 

The kickdown linkage for a 4100 carb is part of the accelerator rod for 66 and up or attached to the intake manifold on 65 and earlier cars. (The same applies for 2100 two barrel carbs.)
Jim

 

I believe the carburetor is for an automatic, the screw at the top of the linkage is the adjustment for the kickdown. A manual carburetor has only the single linkage arm on the primary throttle plates, not a double. If you use it for an auto there should be a dashpot mounted in front of the linkage to prevent sudden closure of the throttle plates when you take your foot off the gas (you can use the thing for a manual or automatic, it makes no difference.) More important is the size of the venturis. There should be either a 1.08 or 1.13 stamped on the same side as the letter/number combination, but in a circle on the bowl. If you have a stock 289 you're looking for 1.08.

What are the markings on the tab?

 

I think you may be correct that it's for an automaticbut it may not be fora Mustang.
JIm

 

I don't think it's a mustang carb. it looks early 70's to me.

 

Is there any reason why it would not work on a 289 mustang?

 

A couple of real goodreasons why it may not work- wrong jets for a start and a few other things that pertain to different size engines. Keep in mind that 4100 were used on engines from 1958 to 1967, from 428 CID's to 289 CID's. You have been asked for the stamped info on the left front mounting ear.With that info, we can tell you whatthe carb was used on and what may have to be changed.
Jim

 

"You have been asked for the stamped info on the left front mounting ear." Yeah, without that info we are stuck in grandma gear. However, basically the 1.08 is the famous and widely used 480 cfm carb and the 1.13 is the not so famous 600 cfm carb.