My 58 ford keeps stalling. I have a fresh engine, rebuilt carburetor, new fuel pump and fuel filter, rebuilt generator, new coil, blew out fuel lines and flushed and dipped fuel tank, rechecked spark plugs, and vacuum lines and all is ok. it dosen't happen right away, usually around 15 mins of driving. I have a new air filter and I checked vent tube on fuel tank and it wasn't clogged. It's not consistant when it happens either. sometimes it bogs down like it wants to die but kicks back on and I can drive another 5 mins or so. Sometimes it bogs down and just dies. I don't know what else to do. What do you guys think?

Maybelle lee