have installed new plugs and wires
idles good but has no power to take off wants to backfire it is a 1979 302 v 8
I would suggest having the carburetor checked by someone who is familiar with those archaic devices. This means locating a mechanic over the age of 50, as the younger guys have either never worked on a carburetor or have very little experience with carbs. It is very possible that the carb needs to be rebuilt or replaced.
You have not yet sufficently inspected your ignition system to conclude your problem lies in the carburetor. Jumping too quickly to the carb. is the mark of a inexperienced mechanic. Remember most carburetor problems lie in the ignition system. Get you engine scoped, then if the patterns all look good start looking at carburetor issues.
1979 302? You might want to check if the timing chain jumped time.
Tester
How was the engine running before you replaced the plugs and wires? Did changing the plugs and wires make the motor run better or worse?
Carbs don’t go bad instantly. If the car was running OK prior to the plugs and wires then you’ve got to go back and check your work. You may have some of the wires crossed up. The backfiring means unburned gas and poorly timed ignition so I think your problem is more ignition related than the carb.
If the truck was running poorly and the new wires and plugs didn’t do much to help then you may have a carb problem.