The "spindle" is the entire shaft that the hub spins on, all the way to the pivot on the axle called the "kingpin". That 8-bolt circle you're looking at is an adapter that holds the outer wheel bearing and spaces the wheel center out to the right width to be compatible with the dual rear wheels. No, it cannot be removed without some very involved (and expensive) machine work to fabricate a wheel mounting flange with a different lug bolt circle.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!