Correct starter for a shortend g-50
 

I am having a problem with starter engagement on a shortened g-50 trans. The starter was replaced with an early stock 915 style starter, this is causing the starter to engage incorrectly due to to the drive being to far away from the ring gear. Because I do not have the old core, I cannot determine the amount of machining that has to be done to the starter nose for correct fitment.Is there another starter that can be used, Or is there a dimension for machining this starter nose.