I have a 79 Bronco and I thought it has an NP-203 transfer case but some of the seals are wrong and the differential looks different from other ones I have seen. So I was wondering how to tell what transfer case it is.

 

It's a NP Transfer Case, but there's more than one // Is it P/T (Part Time) or F/T (Full Time)?

Look on the T/C for a label w/a Ford I.D. number on it, similar to this: D9TA-7A195-GA // Post what it is.

 

The old 203 case was the, what looked bigger full time 4x4 one IIRR
The 205 was the smaller looking part time 4x4 case
The full-time cases were considered crap back in the day and many people installed a different differential to eliminate the full time function and install ed locking hubs
Your Bronco does not have one of those right?
The differential eliminator kits were a cheap way to get part time 4x4 back during the Arab oil embargo and ensuing gas crunches
I installed several
Post a picture of your case

 

That 203 full time case did not come in Bronco or any Fords to my knowledge
I think Google might have it wrong listing the 203 for 74-79 Broncos
I think they are saying you can use either one
The 203 is bigger in the back where the locking differential housing is

 

Dentsides totally came with both the NP203 or NP205. One easy way to tell the difference is to google images of each one and then look at what is in your truck. They look different so you can tell easy enough.

 

D9TA 7A195 KA

Here is what the diff looks like

 

1979 Bronco full time transfer case

1) D8TZ-7B215-E .. Rear Flange Seal - Use with D9TA-7A195-KA Full Time Transfer Case / Obsolete

1) D8TZ-7B215-C .. Front Flange Seal - Use with D9TA-7A195-JA & KA Full Time Transfer Cases / Obsolete

GREEN SALES CO. in Cincinnati OH has both of these seals = 800-543-4959

The other seals are the same part time/full time

 

I stand corrected on Ford not using that full timer