Got my lifters in bits soaking in de-greaser at the minute

Question for lifter experts:5 of my lifters are slightly different to the other 11
The 5 odd one's centres came out easily,but then to strip the centres down to get the small spring out etc I had to lever off a small 'cap' that was holding it all together
Got a receipt with my car for a gen set of lifters,did Ford change the design of there lifters????????
They look identical untill you remove the centre