I'm pretty sure I've got a manual that states how to switch the motor from AC to DC - and yes, the same motor will work for both. Remember, these came out before electricity was standardized in this country (with AC winning) so for a while, depending on your supplier, you may have AC or DC in your home. What I've got says to contact you supplier to ask which you have.
I also have an odd-duck modified 27. It has the godzilla finish and is missing the singer emblem. I'm pretty sure that Singer had a standard that if a store modified the machine, they were suppose to take off the emblem as it was no longer factory specs.