I used the trans-dapt mounts on my '70 dart. Went from a slant 6 to a magnum 360. They fit great and cost about a 1/3 the price of the schumacher stuff and look pretty much exactly the same.
Answered my own question with a google search. Trans Dapt only makes swap mounts for the 68-72 a body biscuit type k frames per their website. Won't work on a 73-76 k