Battery cables

My Barracuda is a slant 6 with out air but with power steering. I know the battery to starter cable runs along the inner fender but the length is what I need. The negative cable from the battery to what on the slant 6 engine block and what is the length?

I am happy to buy the cables on Ebay that are close to factory as nobody I am around has a factory exact piece to go side by side. I want it to look correct as it is a fun driver. I have currently cables from Autozone and they just look silly. I would buy small block cables but worried about length - again I don't know what length to buy because I am not sure of where the negative goes. The positive is easy but I don't know the route as nobody has pictures and neither does the factory service manual. I checks all 800+ pages. No clear pictures of the slant cables for reference.
Joe