I would definately look at the plugs to start with, and see if it's running rich. That seems like the most likely problem. What rear gears does your Nova have? Might also want to check your timing and make sure it's dead on. One last thing. Is your intake heated? Good luck. John.

'68 C-10 - 250 with Edelbrock 600cfm 4 barrel, Offy intake, Hedman headers and true duals, HEI, MSD 6A box, relocated gas tank
Soon to have: T-5 tranny