hey vernon,
well you're wondering about the sizes versus they type material in these other kits you have as to what is actually in the machine your fixing to tear down?
Addressing this i can say most orings are either rubber or neoprene and generally they use standard black rubber or neoprene in these applications. The only time you will see different ones are in cases where there are special chemical exposure or heat related instances where the orings will be colored green or red or tan colored.
The sizes depend on how the engineering guru's designed it, there is no industry standard across all machines built across the spectrum of mfg's, at least none that i've seen in any regular fashion.
One possible way to find out is to go to bigjoe's website and look up the parts and see if they were kind enough to list the sizes in the part description, sometimes they do. If there are 'kits' they generally don't. You can call them directly and give them the model and serial number of the machine your working on and tell them what component your wanting to reseal and they 'might' be able to tell you the sizes but that is a coin toss because they might not be willing to tell you that much detail due to proprietary copyrights that they just don't want you to know. Yeah it does sound trivial but these mfg's are strange like that so you just have to deal with it if they are not willing to tell you.
Can you give me a specific model and serial number of your machine? and be specific on what your wanting to rebuild/reseal? Then i can tell you if there are any surprises you might be looking at that could be considered unsafe or require special tools.
Without knowing exactly what you're working on i'm just guessing here ;o)

I just checked and as far as bigjoe and liftrite they are not the same company, liftrite has it's own website and bigjoe has their own, they do not appear to be affiliated. So you either have one or the other, they are not of the same mfg.