Short answer: many street-driven LS-swapped C10s run reliably on AN-6 feed with a properly designed system, while higher-demand builds often step up to AN-8 feed for more margin. Return lines are commonly AN-6. The real key is not just size — it’s routing, heat management, and restriction control.

“Most ‘fuel problems’ aren’t pump problems — they’re pressure drop problems.”

Practical Line Size Guidelines (Builder Baselines)

Use these as real-world starting points, then size up if your power goals and demand require it:

• Feed: AN-6 (common street baseline), AN-8 (more margin for higher demand)
• Return: AN-6 in most return-style setups
• Filters: EFI-rated only, sized to avoid restriction

What Actually Causes Fuel Pressure Drop

• Undersized lines paired with high demand
• Restrictive filters or fittings
• Sharp bends and poor routing
• Heat soak from exhaust proximity
• Weak wiring and voltage drop at the pump

Routing Priorities (Classic Truck Reality)

C10s run hotter under the hood than most people expect after a swap. Keep fuel lines away from headers, exhaust crossings, and tight pockets that trap heat. Route clean, support with clamps, and plan for service.

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