If the rubber is sticking out like that, the balancer is shot and it explains a lot. You may or may not be able to use the 8" one. Do you know what engine it came off of? That 8" could have been on any internal balance SBC, or it could have come from an external balance 400. You can't interchange them without getting bad engine vibrations. Also, is there enough clearance for the timing tab? If there's any doubt about what you have, then you're better off getting a new balancer. And I wouldn't run your engine any more until you get it replaced. It sure would suck if the thing finally decides to come apart.

 

Here is the spare 8" balancer i had in the garage, do you think i should use it? the # on it is 3942538 i believe its off a late 60's early 70's 350

 

Maybe, maybe not...
I gotta throw another wrench in the gears. There is also a possibility that the wrong harmonic balancer was put on your engine. Your issue might not be with a separated outer ring (yet), although the thing sounds like it's in sad shape. The 6.75" balancer came with either a 12:00 or 2:00 timing mark position (12:00 would line up with the keyway slot, and that's what your year engine is/was supposed to have).
Out of curiousity, check the crank key/timing mark clocking position of the balancer on the engine and on the 8" you have. I can't see the mark in the pictures.

 

The 8" harmonic balancer crank key is at 12:00 and the Timing Tab on engine is at 2:00

 

So the timing mark lines up with the key on the 8"? What I meant on the engine though, is where the key to timing mark relation is on that balancer. You'd need to remove your crank bolt and lower pulley to see it.

 

its off a little

 

OK, that one's supposed to be a little off center, but the one on your engine shouldn't be. You might want to buy a new correct size balancer and sell that 8" one. In addition to being used on the old 350, that # balancer was also put on the 1969 Z28 302 engine. Ooooh! You might be able to sell that for what you can buy your new one for.

 

A friend of mine had a 6.75" balancer just lying around and gave it to me, he said it will work and said it was a off a 1984 Camaro 305, the rubber looks pretty good and its soft, I’m just not too sure about the top dead center mark

 

I'd give that one a shot. The reason the mark is off to the left of the keyway slot is newer engines are more cluttered with accessories on the front of the engine, and viewing the timing tab like you have is nearly impossible. The mark on that one would have been viewed between the water pump and timing cover, but won't line up to your tab.
What you can do, is carefully measure up the damper and with a hacksaw, put a new notch to line up with the keyway slot. Also let me clarify what I was referring to earlier about the 12:00 and 2:00 position. I was referring to the relationship between the keyway slot and the timing mark on the damper (12:00 would mean they're lined up). I wasn't saying that the timing mark would be straight up when #1 is at TDC. I wanted to straighten that out because when the engine is at TDC, the notch on the crank is at the 2:00 position, and that may have confused you when putting the other damper on.

 

Wouldn't a new timing pointer work for him?

All you have to do is remove two of the timing cover bolts and put it on there with the supplied bolts.