Help! Engine dies - fuel system or ignition?

[Lib]

Have a 74 big block - have had no previous problems, but while cruising along at 30 mph yesterday the engine just abruptly died. Pulled over and tried to restart, and it took for ever to fire. Revved it up and held it at 2500 rpm for about 30 seconds to clear it out, but when I slowly allow the rpm to drop anywhere below 2000, it coughs and dies. Then hard to restar again, then same routine. At 2500 rpm or greater, runs fine, so does not appear to be a fuel supply issue. Drop it to 2000, and it slowly sputters, then dies.

Note: ignition was serviced about 4 months ago - new points, condenser, distributor cap, and new shielded wires. No problem since then - until this occurred.

Ideas?

 

[Vettehead Mikey]

Could be the carb float that that's stuck open. Look for leakage when it's idling.

 

[Evolution1980]

I now very little about carbs, but I'll toss this out there for those that know...

Could it be vacuum-related? Or what about his primaries not functioning correctly, like a binding or something when they are barely open?

 

[Hib Halverson]

As the engine begins to "die" is it missing badly?

....running rich?

...running lean or running out of gas?

How many miles on the engine since new or overhaul?