The Problem:
Your 1986 Grand Prix’s factory fuel system was designed to push 5–7 PSI for a carburetor. Your new LS 6.0 needs a constant 58 PSI to fire the injectors. If you try to use the stock lines and pump, the engine won’t even start.
You have two paths here: The “Checkbook Mechanic” (easy, expensive, perfect fit) or the “Hot Rodder” (DIY, affordable, requires plumbing).
Option 1: The “One-and-Done” Solution (Recommended)
If you want to drop the tank once, install parts that fit like factory, and never worry about it again, you want a vehicle-specific module.
The Fix: Holley G-Body Fuel System Kits https://www.summitracing.com/parts/hly-526-24
This kit is a masterpiece for G-Body owners. It includes a completely new sending unit with a high-volume fuel pump already installed inside it. You simply lower your stock tank, swap this unit in place of your old fuel sender, and bolt it back up. It even includes the correct fuel level float so your gas gauge actually works.
• Pros: Factory fit, quiet in-tank pump (fuel cools the pump), reliable fuel level reading.
• Cons: Higher upfront cost.
Option 2: The “Corvette Regulator” Hack (The Budget King)
This is the secret sauce for 90% of budget LS swaps. GM designed the C5 Corvette fuel filter to also act as a fuel pressure regulator. This allows you to run a short return line near the tank and a single line up to the engine.
The Fix: Speedway Motors LS Swap Wiring and Fuel Delivery Kits https://www.speedwaymotors.com/Speedway-Motors-LS-Swap-Wiring-And-Fuel-Delivery-Kits,549267.html?msockid=1ac279c9cf8364c60d2d6f1bce2465f7
You can piece this together yourself, but a kit like this from Speedway or Evil Energy gives you the Corvette Filter/Regulator, the fittings, and an inline fuel pump all in one box.
• How it works: You mount the external pump and the Corvette regulator on the frame rail near the gas tank. You run a short “return” line from the regulator back to the tank, and then a single “feed” line all the way up to the LS fuel rail.
• Pros: Cheap, easy to find parts at any auto parts store, simplifies plumbing.
• Cons: External pumps are louder (the “buzz”); you have to mount brackets to your frame.
Option 3: The Complete DIY Kit
If you want to run your own lines and save money while getting a race-car look, you can grab a universal “Master Kit.”
The Fix: EVIL ENERGY LS Swap Fuel Filter Regulator 58PSI with 6AN PTFE EFI Fuel Hose Kit + 300LPH External Inline Fuel Pump 12V High Flow with 60MM Bracket Clamp https://amzn.to/4rzpnJP
This gives you the filter/regulator and a ton of AN fittings and braided hose. It’s perfect if you are comfortable cutting and assembling your own fuel lines.
The “Garage of Dreams” Verdict
• Time vs. Money: If you have the budget ($800+), the Holley In-Tank Kit is unbeatable. It’s cleaner and quieter.
• The Hustle: If you’re building on a budget, the Corvette Regulator + Inline Pump is a proven setup that has powered thousands of swaps for under $300.
