Lean out and miss fire

Hey guys I have a 66 DART GT w/ 71' LA 408 stroker I have a new balancer, new digital distributor locked out , new wires,coil, plugs, I have check compression and spayed intake and carb for leaks. I cannot get it to run under a load few hundred rpm above idle before it starts to lean and miss and doesnt clear up during driving either. I swapped BLP carb no change and changed MSD no change. It is something we havent been able to diagnos . everything that has been done has resulted no change. weird part it idles perfect. thanks