Ignition or a carb problem?

First off this is awesome site and I wish I had found it sooner!My combination is as follows
- 3600Lbs 73 Scamp (with me in it)
Balanced 10.5-1 .030 over 340
Newer style MP .508 Hyd cam
X-heads fresh and gasket matched with good springs
M1 single plane intake
Edelbrock 800 avs thunder series
904TF with low gear 1st(fresh from SMR)
3.91 8 3/4 suregrip
4000 street /strip tight stall
My problem is that I have bog out the hole but once moving it goes like
crazy.I have shortened up the advance slots on the distributor to achieve
37-38 degrees total with 20 initial using only mechanical advance with 2
light springs.
People have told me the runners are too long on the M1 for a edelbrock avs
but a air gap dual plane would be better suited.
Sorry for long first post but any suggestions would be appreciated!

P.S - The car has went a best of 13.0s at 107 on the motor
11.54 at 118 on nitrous


Thanks Steve