383 Stumble/miss

[StrokedOne]

Hola fellow Chevy men (and women?),

Hola fellow Chevy men (and women?),

I come in need of assistance. I have a 1967 Chevy C-10 with a 383 in her (2 wheel drive auto tranny, no A/C). She has developed a VERY noticeable stumble/hesitation/miss while under load and almost seems to backfire through the exhaust. She seems to idle just fine but as soon as you put a load on her is when the issues begin. I changed the plugs/plug wires/cap and rotor. I have a Crane Fireball digital ignition. After all this I was I got frustrated with it so I decided to take it out to see what it would do. Once I "went through the gears". As I expected it "fluttered" until I let off the throttle... then as I got back down to a cruising speed and pressed the throttle again it wanted to die. I had to feather the throttle for a few seconds before it would get going again. I was thinking maybe a fuel issue but, I just had the carb (Holley 750 vacuum sec.) rebuilt about 8 months ago and then I checked the fuel for water, it's clean.
I'm at a lose here. She was running great up till this point. I first noticed it about 7 months ago but went away for 6 months and just got to work on it. It is driving me crazy. Any help would be greatly appreciated. I miss cruising in my ole truck
Thank you in advanced