All interesting, unfortunately a new block is out of the question. They are not readily available in Australia, they didn't come standard in anything we have.
Looks like I'll take the block to an engine rebuilder, see if I can get number 6 sleeved, see what my options are. If that can't be done then ummm... Might have to concider moving to a 351 small block. But I really want to keep a big block in it