Tyler,
Any pics of the motor mount itself?
If you move the whole engine forward a 1/4" and drill the new holes, and its 3/16" behind the opening now, that would put the backplate at 1/16th" in front of the opening which is where I would think you would want to be. The other option I guess would be to cut off the rails flush with the firewall and use a traditional motor mount bolted right to the firewall.

Warren