Many of the long tube cast headers I've run across had a relief ground on the back side for starter bolt clearance. I just trimmed the bolt on mine. On these new shorty's, they eliminated the heat riser bosses, so they are cleaner on the outside and flow better on the inside.

The C6AE-R's are what is on the existing 352 in the truck. They were used on about all the engine flavors of the FE family, and are known as 428 poor boys because they are similar to the 428 heads but more plentiful and not as pricey. I do have a couple of local sources to check, but the opportunity hasn't presented yet...