If it is not visibly destroying or rotted through then yes. That would be a decent price for just the complete 741 chunk. In my area, I don't see any 8 3/4 rears for anything less than $400-$500 needing a full rebuild. If it is an A body rear or a 67-69 B body, the price usually becomes close to double.
If you want, maybe post some pics and the real gurus can take a quick look at it just to make sure it looks like it wont be a paperweight
