Hyundai Repair: BRAKES, rear disc brakes, wheel hubs

Question
QUESTION: Which brakes can i use from a different model Hyundai to eliminate captive rotor on an Excel X2 LS?
ANSWER: If you were able to do this, you'd need to at least change the wheel hubs and rotors, and possibly the knuckle, caliper, and bearings, which could lead to further changes.  As far as I'm able to determine from the parts catalog, there is no model which would allow you to just switch the hubs and rotors.  Most likely, there's no cost-effective way to do this.

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QUESTION: Thank you for the Quick answer....

I have test fitted the hub assembly from a 1994  Sonata GLE. It seemed to fit nicely but it was a captive rotor design.

I was thinking about the hub assembly from a 1994 Lantra 1.8 GL, is this model captive rotor? I don't mind changing the master cylinder if needed

THANK YOU AGAIN
ANSWER: The 1994 Sonata doesn't use a captive rotor system.  The 1994 Elantra is definitely a captive rotor.  Mostly, you're looking for two things:

1.  The hub fits into the bearings properly
2.  When the rotor is installed on the hub, it fits the caliper properly.

You don't want to change calipers if you can avoid it.  This could change the brake distribution and could make your braking unsteady.

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QUESTION: Is there any model that i would have a chance converting the rear to discs?

Thanks

Answer
Converting the rear will be much harder to do for a variety of reasons:
1.  Hyundais of your vintage rarely had rear disc brakes.  The one that I can think of that did, the V6 Sonata, probably has much larger brakes than your car.
2.  You'll need to actually re-engineer the brake system.  Putting disc brakes on the rear will greatly affect the distribution of brake force.
3.  You'll need to change your parking brake cables, backing plates, master cylinder, and proportioning valves, as well as some brake lines, and maybe the rear wheel hubs.
4.  You'll need to install rotors and calipers.

The cost of making such a switch on the rear brakes will probably exceed the value of the car.