340 has me stumped

Need some input and help,since i got this 1970 340 i have had trouble getting her to run good or consistant.Gas tank is fairly new,vent line clear,new sender /pick up,cleaned fuel hard line with carb cleaner blown through with air then gas blown through with air,dirty now clean,all new fuel hoses,newmechanical carter fuel pump,new edelbrock av2 650(also tried 2 edel 600cfm off working cars)new air cleaner.new fuel filter clear glass type.new plugs,leads,pertronix dizzy cap,rotor,new igniter module,pertronix flamethrower distributor,new coil,voltage regulator,starter/ignition relay,new earth leads,alternator bench tested good,wiring checked and replaced if looking worn.
Just put vacuum gauge on inlet manifold and got steady 22hg at idle,i dont know cam specs but very mild.Idles great mostly,drives great on a 30 mile run,slight bog on wot but nothing too bad,then all of a sudden it will start stumbling and as i appoach a stop sign it wants to stall so i put it into neutrel ,i have taken gas cap off but no better,checked fuel filter and full of fuel,fuel lines not hot,car temp 185 deg,oil pressure good.compression test on all 8 good and even.timing 10 deg -12 deg static checked with 2 strobe lights.all 3 carbs fail the same.no engine smoke or coolant loss.starts first time.it seems a fueling issue,but tried 3 pumps all same.ill try find my fuel pump gauge and see what ive got?Trans fluid level is good and new.trans seems smooth.kickdown needs adjustment again.ive tried to include as much as i know etc,hoping someone has had a similar issue n can help.cheers jon