They are good s/c units, I had a fox for a while with a Novi 2k, Ran with about 16# That was on a forged 306 though. For a stock block 8# would be fine if it was somewhat of a fresh block, but no higher. 6# would be a somewhat safe number but it could be a time bomb. I really think that the stock heads will be very restrictive.
I know you might not want to hear it but Im sure alot of guys will agree with me...
Forget the charger Buy new heads and get a new cam and you might be able to get some new gears for the rear end.
That will wake up your car more then you think.
All the stock stuff will really prevent you from feeling the s/c
Then save up for a even better s/c then the Novi 1k
Dont put the horse before the cart on this one, It is always better to build a foundation and work up. A solid engine will save you time, money, and stress in the long run.
list what is on the car then a plan can be worked out