Small Block MSD Ignition issue

Iv done some searching around on the internet but havnt found anything to solve my issue..

I installed an MSD ignition system on my 78' 360.
6A box, Wires, Pro billet mechanical advance dist. blaster 2 coil..
When i try to fire up the car.. it cranks for a second normal, than acts like the battery is dead.. (which it is not) it acts more like there is a short or something somewhere dragging power down.. but i have been over the wiring of eveything multiple times and cant find anything wrong or causing a short..
I do not have any of the factory ignition parts still in the car, I have great spark going all the way to the plugs..
it has fired for a second a few times but wont keep running.. timing adjustments make no difference, It is definitely something electrical.. I just cant figure out what???
Any help, suggestions would be great!
I know its hard to understand and im probably not explaining things real great but maybe someone will grasp what i got going.
Author: 73mopar360