Your starter looks allot like mine(GM pn 12361146). It came with a round shim that installs in the mounting block between the bearing(that is next to the gear) and the mounting block to move the gear towards the front of the engine if you get my drift. Its used in conjunction with the other spacer you showed in your 1st post. You might get an idea what I'm talking about by checking my pic. The spacer goes into the smallest diameter bore where the bearing seats.
However in all honesty I don't think its wide enough in your case as its only about .050" thick. Two might just clear, but the GM directions call for .100"(+/- .040). FWIW