The fuel coming out of the vent could be several things, but I would recheck the following;
1.) Float setting
2.) Float mechanism assembly, needle to float clip assembly, float tag condition and anything else in this area.
3.) Float to top gasket interference, float can hang up where it comes through the gasket opening causing float to stay to low.
4.) Something stuck in new needle and seat, since the filter inlet was disassembled during the overhaul, a piece of thread material or dirt may have gotten through to the needle and seat. You did put a new filter in didn't you?
5.) Bad new needle and seat, hey - it happens, but it's very rare.
Since this happened after you rebuilt the carb. I would rule out pump and other outside parts.