school me on 67-72 cabs please!

[bigblock73]

I am trying to help out a friend, and would like some help from all of the 67-72 experts on here. Are 67-72 pickup cabs identical and completely interchangable for all years...in terms of sheet metal and such? If not, what exactly are all the differences between the 67-72 years? Also, what about the gas tanks, same size and dimensions? I am not concerned with electrical, gauges, columns and such...just the sheetmetal (inside and out) along with gas tank size and placement. Thanks in advance, I appreciate all your help!