Slugs, driveflanges, full-time hubs, whatever, they all do the same job and they are all somewhat stronger than a lockout hub, the only confusion here came with the issue of external vs. internal hubs.
The internal hubs can be made to free wheel by pulling the chrome cap, retaining ring, snap ring, slug, and spring, and re-placing only the retaining ring and cap (although I'd put the snap ring back on the stub shaft so I wouldn't loose it)
The external hubs can be mad to free wheel by having a spare set of flanged with the splines drilled out, then just pull the tin cap, snap ring, unbolt the flange, bolt up the drilled out flange, and re-install the tin cap.
An those external hubs (often called Dana 44 HD hubs - don't know why) didn't come from any Grand Waggy, they only came on pre '76-ish 3/4-tons with full-time cases, Chevy, Ford, Dodge, Jeep, take your pick, part-timers of that era would have had those funky old HUGE Spicer lockouts that stick out another 5"-6" past the hub.
Once again the Jeep tech section has jumped into the wayback machine and traveled all the way back to no fawking shit day.