I have a ZZ4, been in it since 1997, stock everything, right about 30K miles on it. Still have the 1967 iron exhaust manifolds. Stock 700R4 that drives beautifully but under WOT, hangs 2nd too long and you have to lift a bit to shift.
I put FiTech GoEFI 600 on it for kicks, runs better, but basically the same as the 600 AFB that was on it. As others said, timing is probably the key, I KNOW mine isn't optimal, I have played with it a bit with vacuum, without (as suggested by the paper that came with the engine) vacuum to ported, to unported… But admittedly, I haven't tried hard. And I probably won't, I will just setup the EFI to do it all without messing with locks/springs/weights.
BUT with what I have, and some stuff in the El Camino, it runs high 14s while being super at daily driving. I have a posi, and what I assume is a 3.0x or 3.2x rear. It does pull like it could do better, maybe 14 flat, but I never wind it out that much over 5K. It has 215/70-14 plain jane tires and actually launches okish. Every time I want to make it run better, I get a daily driver that blows it away, and I figure why bother. I'm concerned that if I up the ante on power, that is when I will start to break things like the transmission (we paid $500 for it in 1997) or the 52 year old rear axle, stuff like that.
1967 El Camino Malibu - Deepwater Blue
ZZ4 350, FiTech 600 complete!,Roadmaster tank, 700R4, Underdash A/C in progress, JGC Steering, 1990s truck serpentine.