wont spin

As Demon says, make sure your timing is all in at 2400 rpm @ 34- 36 degrees total. Make sure you don't have any vacuum leaks (leaky pcv hose, intake manifold gaskets, etc.) or an old wobbly distributor. Make sure none of your spark plugs are cracked, it's easy to do with headers. Check your fuel filter.

When did this start to happen? Just out of the blue? After a change? Is it a brand new engine? What do the plugs look like (and I'm talking about the insulator around the center electrode). Is it white, tan or black?

IMO a 650-750 double pumper of the Holley or Demon type would get you rolling quite nicely, but I'm a total Holley guy. I know some that can make a Carter work well, but I can't.