If everyone thinks shimming is a bad idea I'd rather just buy a new intake. I really don't want to go through the hassles of replacing two distributors as I'm running twins. The stock Thunderbolt set up is just fine for my engines.
back in my dirt track engine building days we ran so many cheeting combinations we would machine off the stock collat and add a slip collat to a stock dist..may be your solution if you have access to a lathe or know someone..machine it down,install the slip collar,install the dist,slide collsr all the way down and tighten it and its allen head set screws and use a .020 gasket which will act as the .010 to .015 that the oil pump needs to do its job when compressed..