I have a 67 chevelle 300 deluxe two door post, and its time for a rearend upgrade if any one knows what years (because of width) are a bolt in type swap, or what mods are are nessary for diffrent years? any help would be greatly apprecated

65 to 67 are same width, 68 to 72 are 1/2 wider on each side. All will bolt into the 67. The 65 and 66 will require a retainer (still available from GM dealer) for the spring mounting, but the 67 springs will work.
Bruce

"A" body rearends prior to '66 are an inch narrower, after '67 an inch wider. They will all mount (Oldsmobile I think is different).

Your current rearend ('67) should have the spring retainers. I believe that they will work with the earlier rearends.