"mini" gear reduction starter bolt issues

[69heavychevy]

A few years back I was running a gear reduction starter from a late model Chevy truck. I finally gave up on it and removed it due to always having grinding issues.
I later found out it was because I wasn't using the correct mounting bolts.
Fast forward to present day and I find myself being forced to run the "mini" gm starter again due to clearance issues with a deep sump oil pan I installed.
After researching about which correct mounting bolts to use, I ordered gm part# 12338064.
My issue is the bolt works perfect for for the through hole, but is about 3/8" too long at the blind hole.
Anybody else have this issue?? Is there another starter bolt that has to be used for the blind hole??