I'm restoring my 1972 Charger... When I removed and disassembled the z-bar, I found a rubber coated steel rod inside the bar. I have never seen anything in exploded parts list, etc with this bar. Has anybody ever seen this and what could it be for?

Looks like a backyard repair using heater hose and a metal rod to prevent lateral movement. Maybe a previous owner was missing one or more of the stock parts.

Poor mans torque strap? lol.

obviously a home grown remedy of some sort, but why ?
how was that positioned in the tube ?
was the ball and bushing[s] intact on the bellhousing ?
possibly something to keep the bushing[s] on the ball from falling off and ending inside the tube ?

Speculation........

I'll bet it was put there to keep the Z-bar on the ball studs.....instead of the wire clip that goes over the tube and secures the white plastic half-bushings in the tube end.

The retaining spring may have been broken or lost when it was worked on before you got the car

That makes a lot of sense. The retainer spring was missing... AND the frame rail bracket was broken but still functional. So... I can toss the mystery rod!