67 to 71 frame question

[firedemon]

i reciently found my 67 long bed frame is bent but i found a 71 shortbed frame on the cheap . i thought i read somewhere here the frames are interchangeable with the exception of the core support mounts ? is it as simple as using the 67 rubber mounts or do i change the whole bracket ? or do i use the 71 rubber with the 67 core support ?