The most important changes to me personally are neck profile and width prefrences. Around 67-68' Fender switched from C width 1-3/4" wide thin necks to B width 1-5/8" narrow chunky necks and most of the 68-72'ish P's I have played had thicker necks with the B width which I personally prefer and I think you would also transitioning from a stingray.
My 63' P is wide as hell and really thin with tiny frets which took me a while to and my 71' is in my eyes much more comfortable to play being chunkier, narrower and having the jumbo frets that fender went to in the late 60's.
Tone wise, people dog CBS era Fenders for inconsistency but all of the 68-75' P's that I have played really felt and sounded the same to me and they all really shine with Rotosound 66's. The 65-67' P's with nitro, wide necks and grey bottoms have a different sound and really shine with flats to my ears. The 59-64's are an entirely different animal tone wise. Big and balsy with the up front in your face P tone that you hear on great records. The quality is better IMHO but that being said, I play my 71' as much as I play my 63' and they are both great basses, ones just worth much more due to the rarity.