rebuilding the slant6

What are you talking about? Its a slant,you could run 11-1 and have it ping on 87 and it would still keep running. I shot number 5 rod through the block and still drove it another 160 miles.
That's probably why you threw the rod! :-) I agree that the /6 can take some abuse and has lots of room for perfomance improvements but why go to all that trouble and expense for a grocery getter? The reason they would go a quarter million miles without major problems was that they didn't have enough power to break anything.