1978 302 will not idle

[hotrod5125]

To be straight up on this the carb is on my 51 ford pickup, but i was hoping to getting some suggestions on the problem i am having.The motor is a 1978 302 out of a Mustang pretty much stock.. i bought the truck about 4 yrs ago, one of those projects in a box that someone else gave up on.Any way 4 yrs back i put a new 600 edelbrock carb with mechanical secondarys. It has ran pretty good up till 3 months ago.then one day it decided it wouldn't idle. It acts exactly like it has a vacumn leak but we have check for leaks and tried the carb spray around the carb and alum intake and it doesn't rev up. we have put a rebuild kit in it and all gaskets replaced no difference.It has a cheap odd ball looking electric fuel pump mounted on the frame and no pressure requlator. If you turn up the idle screw it will set there and idle at 1900 just fine but you even turn it slightly down it shuts off immediately.You can drive it ok but if you really put your foot in it for more than 5 sec hard she starts acting like she is starving for fuel and spits and sputters for a mile or so. Trying to make the right decision with money being tight but i will buy a new carb if that is what is needed just hate to put a new carb and find out that wasn;t the problem.One guy told me his edelbrock 600 did this and it has a internal crack/vacumn leak and he had to toss it in the garbage. ALso thought about tying to put a mechanical fuel pump back on there being i belive the motor is about stock and i'am not sure if a ford 302 has a small push rod shaft like the sbc has.Well as you can tell I'am just not sure what to try next, thanks for any help you could give me.If i replace the carb should i go with Holley or Edelbrock and which one is less likely to be effected "inside the carb" by Ethanol .

Thanks Again Steve ( in Ocala Florida )

Steve