I've got a 69 rear end in my 67. The only problem is that the 67 shocks are not staggered but the 69 mounting plates are for staggered shocks. I used 67 plates and it worked OK. Or you can use the traction bars that replace the mounting plates - that's the way my car was when I got it.

I've got a 67 bird with a 65 motor, 69 rear end, 69 front discs, and a mystery chevy orange muncie.