With 3.23 gears and an aggressive cam with that 3000 stall, 340 heads on a 318, you have a recipe for a car that won't pull a greasy string outta a cat's ***.
Here is what's happening. First, your compression is LOW. The 318 had heads with smaller chambers. Installing 340 or 360 heads on a 318 lowers the compression down into the 7s. You're probably at 7.7 or 7.8:1, possibly lower. That's the first killer.
Killer #2 is the "mildly aggressive cam". That cam, coupled with the already dismal static compression, makes any left over cylinder pressure plummet. Goodbye power.
Killer#3 is that converter coupled with the 3.23 gears. What's happening there is, the converter is actually stalling up higher than it should, because it does not have the leverage of a better gear ratio. Converter slip city. If you had 3.91 or 4.10 gears, at least THAT part would be better.
The best thing you can do is several fold. Get some 318 heads back on it. Get a cam in it with around 210-216* duration @ .050". Degree it in.
Then, toss that converter and put a stock one in. You will have a completely different car.
Oh and get those stupid lookin wheels off. Mopars ain't ghetto.
