Brandon,
 
I'm no expert on this, but I've found (talking English - banjo - diffs only):
 
3.54 is Mk2 (BC) 2 litre.
3.77 is Mk2 (BC) 1600.
3.9 exists. Maybe early Mk2 1300.
4.1 seems to be older cortinas - Mk1 or Mk2 (not Mk3 and above, they are completely different).
4.44 anglia?
 
Have also heard that vans might have had a bit lower (higher number) than their equivalent year of sedan due to the need to pull more weight.
 
Autos might also be different.
 
They all interchange if english axle. Axle splines are the same, although I have seen some different tailshaft flanges - think the flanges can be swapped from one to the other. Axles are different in thickness here and there, but in the end, splines are the same.
 
Watch out for the Mk1 escort salisbury style (plate on the back). They are completely different to the English axle.
 
I am sure there are others out there that are much more across this issue (I changed to a Mazda B series diff 10 years ago), but hope this helps a bit.
 
Ash

Okayy yehh, well idk why but in the ford booklet I hve it has the 1.6 sedans, man and auto, 3.54. An the vans a 4.11? But everyone is saying only the 2ltres have the 3.54. Would it be bad if I put a van diff in mine? Would it rev like crazy at 100ks? And also what's the difference between english, axle, and the others?? Sorry I have never dealt with diffs in escorts. So I'm learning.

Some of the early 1600 Ghias with a dual barrel weber had a 3.54:1
 
If you've got a 1.6 I'd go between 3.77 and 3.89 if you don't want it to rev too much on highway.
 
Rhys

Agree. Go a 3.77.
 
They seem to be cheaper too, as they are esier to find than a 3.54.

Well apparently I have a 3.77 now so I'll just try find another 3.77.

Thanks for all the input guys, really appriciate it :)

Brandon.