Man its aggravating when you buy the good stuff and it will not go together right. If you haven't already figured it out, here are some measures to help correct it. First, I'd bench cycle the starter a bunch of times with a battery to make sure the drive is sucking back in all the way. Second, some of the mini starters come with two sets of shims in case of bad stack up tolerances. As previously mentioned don't forget that if you shim the housing back you have to shim the drive back by an equal amount. Here's a starter sold with two sets of shims; http://www.racingjunk.com/Ignition-S...-Starter-.html
You may have to shim the starter and the flywheel with a flywheel shim like this;http://www.jegs.com/i/JEGS-Performan...ductId=1206365
Here are some instuction sheets that indicate .100" (+/- .040") so it may be as close as .060" clearance;http://static.speedwaymotors.com/pdf/910-66258.pdf
Hope this helps you out, thats a badboy flywheel you've got. If you think this is a pain, wait until you get to the clutch engage/disengage part. Out of curiousity,what kind of clutch are you using?