I have a 69 Charger w/ a rebuilt 383. It is .030 over, 906 heads, performer intake, and a holley 650 and headers. THERE IS A PLACE NEAR BY THAT SELLS 110 OCTANE RACING FUEL. I HAVE HEARD THAT IS DOES SOME GOOD to put some in once in a while. Is there an advantage? what does it do for me? if so, what mix to use ???

The race fuel has lead in addition to the higher octane which will help the valve seats if you do a lot of driving. A 906 head 383 can get by with 93 pump gas if compression is held to 10.0 to 1. The open chamber design is prone to detonation if compression is higher and timing more than 34-36 degrees total. If it'll run on 93 without pinging, I wouldn't bother with race gas (most people use a 50/50 mix if they need it).

Smells great!

If you don't need the extra octane, it will produce less power in your car.

No gain to be had in you application just a power loss as too much octane kills power.
you would have to add 110 to every tank to help save your seats not once in a while.
use 93 and get some of this
http://www.summitracing.com/parts/RED-60202/

I have to ask, why would too much octane lower the power output? I would have thought, as least what I have read, that if the engine didn't need it, you were just wasting money. Can someone explain this please?

And because it takes longer to burn more of the burn goes out the exhaust and not forcing the piston.
need's higher compression to be efficient