1967-72 Rear ends for 65?

[bigmoe]

My 65 project currently has a square body 12 bolt rear end in it (open diff). I understand they are 3/4" wider per side and at this point I'm not sure if the width is going to cause me some grief or not. My truck is a Fleetside but the box is not mounted yet in order to do any measuring. I found a guy near me who has a handful of 67-72 trucks he's parting out. I'd like to check them out to see if there's a posi worth snagging. What years are the same width as 65 and what years got wider? And when did they switch to 5 bolt wheels?