$50 isn't bad. You need to make sure it has the carrier caps and the C's at the end of the axle tubes. Is it doesn't have those, it is junk and pass on it even if it's free.
If it has them, then make sure the pumpkin is on the correct side for you. Also measure spring perch width.
If all that is OK too, then it looks like a winner.
The benefit to buying a bare housing is that if you want to rebuild the axle anyway, then this is an economical way to go since you don't buy all the junk you'd later throw out.
I assume you have looked into how much things cost for it right?
Check out ebay for knuckles and SRW spindles. You'll also need the brake caliper mounting bracket (not really a bracket since it's solid cast iron, but you know what I mean), complete kinpin parts, steering arms, axleshafts, carrier, gears, hubs, wheel bearings, axleshaft seals, carrier seals, spindle nut set, diff cover.
The list goes on and on BUT if you plan on 35 spline, detroit or ARB, replacing WB and kingpin junk anyway, then again it is a good deal.
-- Mike