I have found the answer to this question just in case anyone is interested.
The proper length for side post battery cables are the following:
Small Block (302, 307, 327, 350) - (Positive is 43-3/4") and (Negative is 34-1/2")
Big Block (396, 427) - (Positive is 45-1/2") and (Negative is 29-1/2")
The main length of the cables are black regardless of positive or negative with the "heads" that contain the bolt that attaches to the battery color coded in red for positive and black for negative.
Hope this helps.