Ike-
I know other people have had the same problem using MSD distributors and have fashioned spacers to solve the problem. Pat Buckley is one that I remember said that he had that problem. If you do a search you should be able to find at least one or two different threads discussing this problem. If you can't find it, send Pat an email and I'm sure he'd be happy to tell you what he did to fix it.
Get that thing started already, it's the middle of May already, what are you waiting for?
Mike