Slant 6 to 340 swap
Here is what I think I know,
As I am thinking about doing this in a 65 dart.
You can get motor mount brackets, so you dont have to change the K-frame. I am not sure who has them, but I have seen them on ebay.
Your brakes will most likely be 9 inch, so that needs to be upgraded.
A bigger radiator would be nice.
Probably should replace the springs and torsion bars.
If the car has power steering headers are going to be a problem.
Need a bigger rear end. The 7 3/4 will not last too long behind a 340.
You are probably going to replace the rear mount and driveshaft.
So plan on replacing the entire drive train and brakes.
I am sure I am forgetting more than I know.