Issues with Holley 600 on 67 with 289 engine

Issues with Holley 600 on 67 with 289 engine

This car sat for about 15 years and a couple months ago we started getting it back in shape. It runs now but the carb is still not right.

It was re-built by my friend (not a professional mechanic) and clean out with carb cleaner and we put new gaskets and such in there.

The problem is if the car sits say overnight it will not start. If we pull the front piece off the carb and clean it out it works. We had a float on the front section that was sticking too. We ended up putting the old one back on.

If you get the car going (pull front piece off or knock the float down) it will run great. And after it is warm it starts right up.

This car had an autolite 4100 or 4300 on it and this Holley is off a different mustang (which has also sat for a while) but it should be fine right?

Any ideas on getting the carb working better? Any other ideas for the car/carb to work around this situation?

The needle was definitely sticking. We had a brand new one and the old one and the both stuck. Do I need to go by a 3rd one (maybe one in rebuild kit is bad or got messed up)?

Where can you pick up just this needle?

If the needle is bad or messed up why does it work after you get the vehicle running? Seems like once the vehicle has run and the engine is warm and all the thing works great.

I see this
Advance Auto Parts: Needle and Seat Assembly HP by Holley - Part 6-506

Which is the part that is sticking. Would it make sense that the one in the rebuild kit would stick too? Or is there something else wrong with my carb or setup?