NEED help, 78 power wagon 318 to duster?

Looking to purchase a 318 from a 78 power wagon today, and its avail for today only, I need to know if this will fit in my 75 duster, was stock with a slant six so I know I need the mounts, but what else? and will it still work with my 904 trans? I dont want to buy a motor that will be useless to me! Any and all help will be great! Thanks fabo