Help with timing mark

[chargd72]

How do I read this timing setup?  The engine is a '76 400.  The truck runs good when warmed up but I get a lot of miss-fires until it reaches operating temp. 

There is a little diamond shaped hole in the center (red circle) that I assume is 0.  At idle, I have it set at the red line because that was my best guess at 5 degrees btdc. 

Sorry for the poor photos

[Chryco Psycho]

I would time it by ear , bring the rpm up to 3000 or os and advance until the rpm quits rising & back it off util you can just hear the rpm drop , if it pings back it off slightly

[chargd72]

Thanks, would I keep the vaccum advance connected while doing this?

[Chryco Psycho]

generally I have found that they run better without using the vacuum advance so yeah I would leave it off
but if you are going to keep it connected you can either dial out the amount of advance with an allen key inside the vacuum pot on the dist so you get enough advance at idle [typically about 14* ] without over advancing at high rpm