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The box is ok I have driven the car the bolts are from the old starter motor that was in it what does the shim doHi and welcome to the forum.
I suggest you post one comprehensive thread with all the relevant information rather than posting multiple threads which is against forum rules. That and a little patience...
It also sounds like you have used a later model transmission, there are a couple of other members who have done this, hopefully once they see this thread they can chime in.
Also, are you using the correct bolts for the starter? Some starter motors also have a shim between the starter and block, if there is no shim I would try adding one and see what it does.
Really? I'd say a decent performance shop should stock various shims as a lot of aftermarket style starters need them to make them fit properly. Or go to the wreckers and pull one out of a Commodore there.If you find a shim let me know. I need one but haven't been able to buy one, they have become quite rare.