* Your intended use: Are you looking for maximum horsepower, improved fuel economy, or a balance of both? A heavily modified engine will need a different carb than a stock engine.
* Your budget: High-performance carburetors are significantly more expensive than stock replacements.
* Your mechanical skills: Some carburetors require more tuning and maintenance than others.
That said:
* 2-barrel (or single-barrel): A 2-barrel carburetor will generally be more fuel-efficient and simpler to tune than a 4-barrel. It's a good choice if you're looking for a reliable, reasonably economical setup for a stock or lightly modified engine. They are also generally less expensive.
* 4-barrel: A 4-barrel carburetor will typically provide more horsepower and torque, especially at higher RPMs, than a 2-barrel. However, they can be more complex to adjust and may consume more fuel. This is the better option if you're looking for performance gains. This is particularly true if the engine has other performance modifications.
In short: For a stock or mildly modified 1979 Ford F-150 400, a properly rebuilt or replaced 2-barrel carburetor would likely be a good starting point for reliability and fuel economy. If you're aiming for significantly increased performance, a 4-barrel is necessary, but expect more complexity and fuel consumption.
Before making a purchase, carefully consider your needs and budget. Consult a reputable parts supplier or mechanic experienced with these engines for specific recommendations based on your truck's condition and your goals. They can help you select the right carburetor and ensure it's properly installed and tuned.
