Help!! im confused!!!!

well I guess I can start off with, I hear of 60mm turbos and 67 mm turbos, then gt45 and t60 t66. what size are they referring to exactly?? I would like to use a set of the gt45's off e bay for startes then if they fail upgrade to something better. Im planning on staying injected and running the comp 274 cam on forged internals possibly 392 stroker.
14 lbs of boost. ok now i need opinions.....
DON'T BUY EBAY CHINESE GARBAGE.

Ok in order to select a proper turbo there are must have details.

How much power are you wanting, honestly?

Drag car, street car, or street/strip car?

What rpms are you intending to spin?

Single or twin? Twins is more expensive