Joined: Nov 2016
The differences for the K-code Mustangs are mostly internal. The stamping and date code won't tell you. Even the crank is a cast piece, though it had to pass a Brinnell test for hardness. The heads are essentially the same as other 289s too, except for threaded studs. If it doesn't have solid lifters, that's a dead giveaway. And of course, they got special cast iron 'headers' that are marginally better than the old logs. Unless your car has a "K" in the VIN, it's mighty unlikely that someone would transplant a K (Hi-Po) motor into it.
I smile a lot. It makes people wonder what I'm up to...