Starter motor solution for a flywheel that was moved back 1/4 inch.
One solution comes from post 16 above:
"We left the flywheel in the stock position,we left the ear on the adapter plate to align the starter.and we machined a new outer shell to hold the pilot bearing to make up the .125". We removed the factory block shim so the new output shaft location is .125" further backward closer to the rear. We found that the driveshaft slip yolk had more than enough room to accommodate the new location."
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Without seeing your stuff on the bench where things can be measured......

If a starter is forward of the flywheel....
Another solution to move a starter motor back 1/4 inch to engage the flywheel,
is to machine 1/4 inch off the starter mounting ears, so the starter goes into the bellhousing hole 1/4 inch further
and keeps the starter-to-flywheel distance the same as before you started.

Plan B is to buy a new high performance starter and do whatever is needed to space the starter gear on the flywheel teeth properly.