Factory Rear End

[Mjminino]

When I purchased my truck it was in such shambles and I don't know if a lot of stuff is 'factory', they did a $hit job on the front end converting it to a 5 lug, which I was able to get that figured out. I am about to purchase some Impala SS brackets from Captainfab to get rear disk brakes, and get the CPP 5X5 rear axle conversion for a 64. Well in all honestly, it just dawned on me, I don't know if I have a 1964 rear end or another later year (if they took the same front/rear suspension off of a later truck) Could you guys please help me out on figuring out if this is a 64 or not?