73 kframe on 72 abody
Don't file/grind the holes!!!
The K frame not fitting is a symptom, not the problem.
Sometimes the K frames can be a little interesting to install, make sure you have it well supported with a jack, then you'll want to thread one bolt into the frame and leave it very loose, not even up to where the shoulder of the bolt widens. Then you can use a pry bar or similar to work your way around the K frame until all of the other holes line up. They don't have to be perfect, you just have to be able to start all of the bolts. The shoulders on the K frame bolts will take care of the rest. I usually like to jack the K frame up until there's just slight pressure on the frame, then start working with the bolts, but sometimes you might have to drop one side down a little to start the bolts. Make sure the car is supported evenly, if the body dolly or jackstands aren't level they can make your life a lot more difficult. Some are just more difficult than others.
If none of that works, check your frame and K frame dimensions. You can download a body service manual for your car here MyMopar - Mopar Forums & Information - Service Manuals
And this is the chart with the measurements you're looking for. For some reason I can upload a much larger picture if it's tall (not wide), so turn it sideways after you download it. :D
Don't file/grind the holes!!!
The K frame not fitting is a symptom, not the problem.
Sometimes the K frames can be a little interesting to install, make sure you have it well supported with a jack, then you'll want to thread one bolt into the frame and leave it very loose, not even up to where the shoulder of the bolt widens. Then you can use a pry bar or similar to work your way around the K frame until all of the other holes line up. They don't have to be perfect, you just have to be able to start all of the bolts. The shoulders on the K frame bolts will take care of the rest. I usually like to jack the K frame up until there's just slight pressure on the frame, then start working with the bolts, but sometimes you might have to drop one side down a little to start the bolts. Make sure the car is supported evenly, if the body dolly or jackstands aren't level they can make your life a lot more difficult. Some are just more difficult than others.
If none of that works, check your frame and K frame dimensions. You can download a body service manual for your car here MyMopar - Mopar Forums & Information - Service Manuals
And this is the chart with the measurements you're looking for. For some reason I can upload a much larger picture if it's tall (not wide), so turn it sideways after you download it. :D