96- 97 is transition year. GM parts giant splits the switches between Axle RPO Codes.
15552842 - ZLS, ZLT, ZLW. Three wire
15731298 - ZWA, ZWB, ZWD Two wire
Also, replacement parts my appear different, but look at the body housing that screws into the axle. The thread and tube are same length.
I don't know what criteria you used to find your parts.
If your not real familiar, if you go to " GM Parts Giant " enter the complete VIN of your truck , it's GM , they know what your truck was built with, by serial number. Select part boxes for front differential it will have the listed parts for your truck. Not a broad span of , but yours.
The other reliable choice is " AC Delco Parts " the real one , same thing enter by VIN , the dealers actually would search that way, faster, more reliable.
Good luck.
ps. Model- Tahoe, Sub, C1500, K1500, C3500 and so on.
We can help if we know what you have.