The nipple can be hack sawed from the inside with a blade holder. Cut 3 or 4 slots into the pipe stopping when the threads from the manifold get close, then use a small chisel to chip the sections towards the center of hole. You should use Liquid Wrench ahead of time to penetrate the threads. Use a pipe clean up tap.
Another way is to tap a solid rod or chisel into the pipe first, then grab the outside with vice grips. This will prevent the tube from collapsing before you can budge it. Again the Liquid wrench must be given time to work first.
Lastly, you can drill out the remains of the stub then re-thread.
Thanks Aracer. Followed your advice and got the last piece out and save my factory manifold. The threads will need to be cleaned up but definitely can be reused.
Replaced a cheap fuel pressure regulator (brand new and leak) with a much higher quality unit today. Checked engine timing and tuned the carb. Engine was initially running real rich and could not set idle. Turned out engine was running at 40 degree advance (suprised engine starts at first crank). I must had bumped the distributor when working on the new manifold because timing was good before I started. Everything set now with engine idling at 750 RPM, 17 in-hg vacuum steady, 8 degree initial advance and total all in at 38 degree around 2500 RPM. RPM gauge is acting werid showing 2000 RPM when idling at 750 RPM (timing light). The gauge behaves normal when car is at freeway speed.
Car drives good and no ping. Next week I might disconnect vacuum advance and play with initial to get 36 degree total based on CP's recommendation on other threads.
Work completed under this phase includes new Edelbrock RPM Air Gap intake manifold, 650 AVS Performer Carb with dropped base air cleaner, refurbished throttle linkage, fuel pressure regulator, new radiator, overflow tank, new washer bottle and pump, replaced all hoses, caps and rotors, new ignition coil, ignition wires with irridium spark plugs, oil catch can and new engine wiring harness.
I drove the car for about 12 miles of street and freeway. Already I can see the oil catch can (cheap one) is already working and my new carb and intake are protected. Engine definitely feels stronger and smoother. Acceleration is good but will need to adjust the kick down linkage. Transmission does not kick down at full throttle. Also no more problem of engine stall when braking hard
Next phase: underside of the car, install flexplate cover and deep transmission pan (new filter with extension and change oil), clean and grease suspension, U joints and change differntial fluid.