I have a stock 350 with a 1405 Edlebrock Carb and a Edlebrock Performer Manifold.
I have recently installed a set of Edelbrock Aluminum Heads number EDL60999 64CC, a Comp Cam HE (High Energy), with 212/212 and a .440 x 440 Edelbrock chain and gear.
Idle and cruises fine at 1500 RPM, any higher seems to lose power, sometimes, when cruising I let off the gas and the motor shuts off. If I wait a few minutes, the car starts and I rev it up a little and drive away. I am only driving it around the block because I can't trust going any further from home. Need Help PLEASE!

Check your ignition timing.

Check your ignition timing.

........ and check your fuel pump, fuel pressure and fuel filter. you could be running the carb out of fuel. ensure your floats are set properly. When you are at 1500 rpms you are probably still in the idle circuit and once above that you could be running out of fuel starving/leaning out the motor. Also check for vaccum leaks since you just changed heads. end gaskets and manifold gaskets.

Timing is set at 12 Degrees Before Top Dead Center

That isn't enough timing, was it set with vacuum applied to the advance unit?

No, Vacuum was disconnected to set timing.

what fuel pump are you running ? any regulator? whats your total timing / advance curve? at what rpm is your mechanicle advance all in? ideally you want 36* all in by 3000 rpm. if you have a stock dist. they have 24* degrees mech. advance. with your 12* initial you shoul be there.....you may have too much vac. advance try diconnecting and plugging it see if your loss of power improves. let us know

Thank you everyone, for your input sorry it took so long to report back. Thank you Brian you hit the nail on the head with the Float settings, they were way off.

I took the carb apart and found floats not set properly. Set to specs for carb, cleaned and put back together. The car is still cold blooded takes several attempts to start when cold. Shuts off, I pump the gas and its starts shuts off...etc. after manually closing the choke the car stayed running. I got it to operating temp 185 Degrees, in park I stepped on the excelerator, it spit through the carb and shut off, I pumped the excelerator one time car started and shut off again. Everything is the same as in the first post. Timeing, getting fuel, fresh gas, no vacuum leaks (if I place hands over the carb it will kill the engine) "vacuum leak test." I have worked on over ten Chevy 350 engines, valve jobs, cam replacement, timeing chain and gear replacement, overhauls. In over 35 years I have never had a problem restarting an engine after service. Again PLEASE HELP! THANK YOU ALL!

If you spitting through the carb, it is a carb or timing issue. Assuming your valve train is set correctly. If you are positive that thier is no issues with the timing i would go right back to the carb. Is the carb new, or used? If it is used, it may be time for a complete rebuild (by a professional) or a new carb. If you have a good working spare around put it on and see if it does the same thing. If it does we can adress other issues. If it solves the problem then you know its the carb.
Do you know how adjust choke on carb?

Fuel level in the carb is not correct. IE: "Float Setting"

My Bet!

AL

Was it a plastic or brass float?

Did you check it for air tightness? (i.e. float it in gas)

Is the fuel inlet pipe ejecting fuel as you start it? It may have loat its prime, and you're pulling air into your system.