It should work no problem.  You will ether need to mill the extra material off the top of the steering arm (I have done it twice and simply used an angle grinder)  or you will need to use T-bird tie rods.  The OEM gal tie rods will fit as is but you will not be able to get the nut tightened far enough down to insert the keeper pin.

In 77 Ford started using a slightly different spindle that came on the LTD II and I believe all the other cars using the same spindle design including the t-bird (could be some year overlaf fotr the older design as Ford used up old parts).  The newer spindle is almost identical to the previous one except the steering arm went back to the thickness of the early 60s drum brake spindles, meaning you can use a 60s era tie rod and the manufacturing tolerances were not as tight as previous years because these donor cars had more alignment adjustment.  This means some spindles work and there are no camber issues and some do not.  I have LTD II spindles on my Galaxie and setting the camber was not an issue.  If you get spindles with camber issues than you need to totally relocate the UCA mounting bracket which is a bigger job than one might think.  It has been my experience that the newer spindles work with out issue two out of three times.

Here is a repost of some general disc brake info it doesn't address the potential camber issues I already mentioned.

Daze wrote:

If you want "junk yard" disc brakes, a really good option is to get them off of: 

1974-1979 Cougar 
1974-1978 ford pass 
1977-1979 LTD II 
1974-1976 Montego 
1974-1979 T-Bird 
1974-1976 Torino 

All of these cars should interchange with your Galaxie with little or no trouble or modification. Just be sure to grab all the parts from one car so you'll have a matched system. Also any disc brake system from any car in the "galaxie family" other than the ones above should fit however with early 70s cars you will probably encounter one issue, the steering arm on the disc brakes for later Galaxies (not listed above) including the LTDs and country squires is thicker than the standard Galaxie steering arm so when the tie rod goes through the hole you will be able to install the nut but not the pin. the fix is to grind about 1/16" to 1/8" off of the top of the steering arm. I did this on a pare of brakes I sold and all worked well. 

Sanddoc wrote:

Daze
what about swapping out the complete steering linkage from a mid 70's  idler, center, end etc: 

 

I don't think it would work very well.  Yes the spindles are the same but the draglinks are a lot different this matters because the drag link determines inner tie rod spacing and said spacing is a lot different between the two types of cars.  Why this is important is because the inner tie rod placement effects steering arc which has to be correct or you get bump steer.

OK, i am really starting to panic about this offset hole issue on the spindle for the upper ball joint on some T-bird spindles creating camber issues. I got the spindles on today and everything went good. I checked the hole for the upper ball joint on the spindle and it appears to be centered. Did some quick measurments, seems ok. I couple of issues I have come across are: The splash shields have a loover to direct air onto the rotors, those come in contact with the lower control arm when rotating the spindle. Will need to trim those. Secondly, the brake hose leaving the caliper which is from the T-bird, exits the caliper towards the front of the car and almost comes into contact with the castle nut on the upper ball joint. Suggestions for what type of brake hose to use?
Anyway, i did a ton of research before doing this swap, checked a bunch of forums and everybody that did this swap had success. I hope I will also.

Looks like you did a nice job.  It's a little late now but here is the parts list that came with my LTD II swap.