will the 2012 Deluxe rear fender w tombstone tail light swap out with a 2012 Heritage rear fender? I cant tell if the fender bolts line up on the fender strut...

 

I'm sort of in the same boat; trying to fit a Deluxe rear on my slim. After my research, I'm pretty sure they do. (in your case)
Best advice is to go over to a dealer and take careful measurements of of bolt positions etc.

 

I am also considering this mod, but has anyone put the tombstone light on a Heritage fender?

 

A Softail fender from same year ranges should bolt right up...but
a OEM type Heritage fender with come with cut out thats more horizontal than vertical. Which would lend it self most suited to the wider stock brake light. If I were gonna run tombstone I'd start with a full fender and just cut hole for tombstone.