Hydraulic lifter help

[59belaircopcar]

Hey guys,

I picked up a set of lifters from AutoZone for a 1965 283 SBC. Is "Melling" a decent name brand? Anyway, got four identical boxes with p/n JB-817. Right off the bat I noticed 8 of the lifters had gold colored retaining clips and the remaining two boxes had silver colored retaining clips. On closer inspection I noticed the gold clipped lifters seat was closer to the top of the lifter body (.105) and the silver colored clipped lifters seats were further down in the body of the lifter (.185). These measurements were taken from the top of the lifter body to the outside diameter of the lifter seat. I have included a picture. Other then that they are identical in outside dimensions. Oh one other thing. The silver clipped ones I can easily push the seat through it's travel with a push rod. The gold ones are rock solid. I did install them and turn the oil pump with a long screw driver in an attempt to "pump" them up to see if they would get hard. They did not. But I don't know if that method would be enough to pump them up? The boxes appeared to be new and unopened. What should I do? I'd imagine they would work once the valve lash was set. But it just doesn't seem right to have different lifters. Any thoughts?
Thanks,
Kevin