410 Compression Test and tuning.

Hey Ty,
No 8 does look darker.If you put those plugs back in,
put no 8 in cylinder one to see if it burns clean.Swap plug wires 8 and 7.
If after running plug one is still dark it is the plug.
If plug 7 is darker it is the plug wire.
Look closely for carbon tracks on dist cap !!!
Have You tried blowing out the old tranny lines with compressed air/brake clean?
If you get them clear you could continue diagnosing...