I just went through this same process, except my tcase was broken, not just leaking. I ended up finding a used 80k mile one on EBay for $190 shipped, which I thought was excellent.
If it's just leaking, I would split the case and reseal the halves or install new seals on the outputs. It sounds intimidating, but it's really not that bad. I just split open my busted one and now that I've seen the inside of one, its not complicated at all. The only thing that seals that case halves is RTV, and there are 5 other seals (2 outputs, 1 input, the shift selector, and the case front adapter, which can be replaced with RTV). If you know which seal is leaking you can fix it for anywhere from $5 (RTV) to $30 (output seals aren't cheap).
If you still want to get another one, you have to be picky about what it comes out of. The Hollander exchange information for our trucks is as follows:
EXPLORER 01 4x4 (part time, electric shift), 2 Dr (Sport)
EXPLORER 01 4x4 (part time, electric shift), 4 Dr, Sport Trac
EXPLORER 02 2 Dr (Sport), ID 1L54-AB
EXPLORER 02 4 Dr, Sport Trac, ID 1L54-AB
RANGER 01-03 (Warner 1354), electric shift, ID 1L54-AB
These are direct bolt ins, shift motor included, without any extra sensors or wires.
Now, if you want something that can work, you have a lot of options. Mechanically, a 1354 is a 1354. All the guts are interchangeable, the only differences are manual or electric shift. ANY 1354 will mount to the back of your transmission. The differences are in the output yokes.
The majority of 1354s come with the flat flange rear output yoke like you need, so this is generally not a problem. The main thing to look for is the front output. On older models, the front drive shaft output uses a standard U-joint yoke, to which you bolt the u-joint cups with straps. On newer model trucks, this was changed to a cup style output to accommodate the factory CV type front drive shaft. If you want to use your stock front drive shaft, then you'll need to find a transfer case with the "cup" style front yoke. However, I saw that you are working on an SAS, in which case a standard front yoke would probably be more useful since you're probably going to need a custom drive shaft anyway.
The only other difference in 1354s is electronics. Older 1354s has speed sensor outputs as well as a brown wire leading into the back of the case (not the same brown wire as found on 4405 transfer cases). If you use an older tcase in your newer truck, you can simply disregard the sensors that you don't have a connector for. The transfer case will function just fine. Newer 1354s like ours have no sensors or electronics other then the shift motor. The holes are generally there, but the castings aren't drilled/tapped for anything.
Lastly, if you want to go to a manual shift 1354, make sure that your transmission has the threaded bosses to mount the t-case shifter to. Some of the newer transmission no longer have these since manual shift t-cases are few and far between anymore. If you get a manual case, and have no place to mount your shifter on the rear of the transmission, you'll have to rig up your own shifter as Ford parts won't work.
In summary:
Any 1354 will bolt to the tranny.
Almost all 1354s will bolt up the rear driveshaft
Old 1354s (pre-98ish??) have a different front output then the newer ones.
Old 1354s have sensors that the new ones do not.
1354 parts are 95% interchangeable
