Swifty, I would take the advise these guys are giving you. I am speaking from first hand knowledge. My 69' Cuda's block was in bad shape, no where near as bad as your block. My 340 had a few minor scratches in the cylinder walls about .060 deep scratches. I ended up cleaning the motor up, Sleeving all 8 cylinders, new pistons, rods, cam, etc. except I was able to keep my crank. In the end my lower end cost around $4400 after all the machining and parts.
Here is my block before the work http://i1009.photobucket.com/albums/af213/eldaron01/DSC00730_zps475356b0.jpg
After the work: http://i1009.photobucket.com/albums/af213/eldaron01/2477_zps823f9c5b.jpg