tail light assemly

I havea 74 swinger that I have been working on for a little while now.
As most would know the 74 and up diplomat style rear end is as un musclely as you can get. I am going to attempt to change it out for 73 or earlier, has anyone done this or have some advise on the swap. I'm not sure but even a 69-67 swap??? Thanks for the help n8o