C-10 trucks were manufactured with 6 bolt hubs. The 8 lug hubs and wheels were installed on C-20 and C-30 axles, so either your axles have been changed, or you've got a C-20 truck with C-10 badging on the vehicle. "Lock ring" rims are made for tube type tires, and the center of the barrel section of the rim is straight, affording clearance for larger brake drums. Drop-center wheels designed for lighter duty tires and/or tubeless tires will not clear the brake drums on some heavy duty applications. The "widow maker" wheels that are dangerous to run were 20" diameter, with a tiny locking lip in the middle of the two wheel halves. That design was never used on 3/4 ton or 1 ton trucks, IMHO. Removable lock rings at the outer edge of the wheel are safe, as long as they're not badly rusted or damaged where the lock ring fits, and they're assembled and inflated correctly by someone who knows what he's doing. Split ring wheels cannot be used with tubeless tires- - - -they won't seal the air well enough for the tire to stay inflated.
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!