Thanks, that's good advice. I have a passenger drop bellhousing for the early style 4500. I was hoping to not have to buy another bellhousing, but the early 4500's are even harder to find than the later models. And since I'm using a doubler, the extra low granny isn't as important.
I also see now how you solved the problem of the one hole on the 203 range box which didn't seem to fall on the flat part case. You just skipped that one right? (ie, only drilled 5 holes?)