124 '87 rear axles

[toknow]

There is a clicking sound from the back, when driving uphill...
I think it is the axle. There are several options:
1. replace with rebuilt ( from any auto parts store (@ $150)
2. replace with new from fastlane ($460)
3. replace only the c.v. joint (inner) ($80) and the boot etc..but how about the outer joint? does the inner fails more often?

please advise on which option, the car 1987 300D, has 175k miles and drives good except this clicking.
thanks