7 1/4 rearend
Maybe I'm an exception to the rule but I ran a 7 1/4 posi in my '67 Cuda on the street behind a mild 318/727 & later behind a strong 360 until I got an 8 3/4 & never had any problems. I'm not recommending it - just sayin'.
Now running a Dana 60/ 4:88s behind a RB!