Has anyone seen a blue print or some kind of a wiring layout for a 68 chevelle ss.All I'm doing is adding a tach & new dash wire harness.I can not find any books to show how to put the dash back together or wiring layout???Also need to know where tin ground straps go to?

Assembly manual has them. Any ressto parts house can sell you one. There is a small pamphlet they sell too just for wiring but IIRC it is the same stuff in the Assembly manual.

If you're using a reproduction wiring harness, like the ones from M&H, I'm not sure you need any instructions. I've done it, and it's pretty much plug-and-play.