Urgefor,
Do you need the C5 and/or the bosses for a specific reason?
Mostly to make my life a bit easier.  I have a '64 block with the bosses but the project car is a '66. I've fabricated some motor mounts to make it fit but it just "bugs" me a bit. Long story short, I was not aware some C5 blocks were cast like that also.  If I can get a C5 block with bosses and extra material in the webs like the '64 block along with the 4 bolt engine mount pattern, it would be a win/win for me.  I have a couple C6 engines.  To be more precise, one engine (from a country squire) along with a complete drivetrain from a '66 Galaxie that was a real man's car.  4bbl, 4spd, no air, no power brakes and no power steering.   
