I don't think the crankshaft bolt pattern stayed the same when the swap was made to the 230/250/292 series, or the V8's. Does the flex plate have a welded-in center piece with the 261 bolt pattern? Maybe the flex plate is installed backwards. The regular shims for block-mounted starters do not change the fore/aft position of the starter- - - -they only affect the depth of starter pinion gear engagement in the flywheel ring gear to prevent the teeth from bottoming out. If the starter gear is touching the flex plate it sounds like the adapter is made wrong or you've got the incorrect starter for the application.

If you need to shim the flex plate further toward the transmission to provide more starter pinion clearance, just use the original 261 flywheel as a template to get the hole spacing you need, make some circular shims from soft aluminum about 1/16" thick, and stack them up as needed between the flex plate and the crankshaft.
Jerry


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