G-Body LS Swap: Real Cost and Every Part You Need
A junkyard 5.3 into a 1978–88 G-body (Monte Carlo, Regal, Cutlass, El Camino) comes to about $7,120 with used parts and your own labor, or about $13,820 with new parts and a shop doing the work.
The G-body is one of the easiest LS swaps there is: mounts, oil pans, headers and crossmembers are made off the shelf. Here's what four common builds cost, from a mild junkyard LM7 to a turbo street car.
Four G-body builds, priced
| Build | Crank | Wheel | 1/4 mile* | Used parts, DIY | New parts, shop | |
|---|---|---|---|---|---|---|
| LM7 5.3, stock, 4L65E | 305 hp | 250 whp | 13.11s | $7,120 | $13,820 | Open |
| LM7 5.3, Stage 2 cam, 4L80E | 375 hp | 308 whp | 12.24s | $8,395 | $16,963 | Open |
| LM7 5.3, single turbo 8 psi, TH400 | 427 hp | 350 whp | 11.73s | $11,200 | $23,223 | Open |
| LM7 5.3, cam + turbo 12 psi, TH400 | 568 hp | 465 whp | 10.66s | $12,868 | $26,693 | Open |
The gap between the two price columns is mostly labor (about 34–55 shop hours) and buying the engine, transmission and turbo used. That's how most G-body swaps actually get built.
What fits a G-body
Oil pan
The stock truck pan hits the crossmember. Builders use the GM muscle-car pan (19212593) or a Holley 302-2, which Holley lists for the G-body. SummiteBayAmazon
Transmission and crossmember
Hooker's 12644HKR crossmember fits the TH400, 200-4R, T56 and T56 Magnum directly; the 4L60E, 4L80E and 6L80E each need a specific adapter. A 4L80E fits once its case "ears" are trimmed. A T56 needs tunnel work and a shifter hole, and a 6L80E needs major tunnel work. SummiteBayAmazon
Rear end: the part that breaks
Most G-bodies came with a 7.5-inch 10-bolt. It's commonly run to about 350 hp on street tires; sticky tires, launches and weight all shorten its life. Past that, builders swap in an 8.5-inch 10-bolt, a 12-bolt or a Ford 9-inch. Strange lists bolt-in housings by vehicle.
Parts people forget on a G-body
- Driveshaft shortened or new, with the right slip yoke (4L80E and TH400: 32-spline).SummiteBayAmazon
- Speedometer fix. G-bodies have a cable speedometer and LS-era transmissions send an electronic signal. A Dakota Digital ECD-100 turns it back into a cable drive.SummiteBayAmazon
- In-tank fuel pump that holds about 58 psi. The factory carbureted fuel system can't feed an LS.SummiteBayAmazon
- Steam tube kit for truck engines going into a car radiator.SummiteBayAmazon
- Gauge adapters for oil pressure and coolant temperature.SummiteBayAmazon
- Transmission cooler and lines for any automatic.SummiteBayAmazon
Sources
- Holley 302-2 LS swap oil pan
- Lateral-G: Holley LS oil pans, which one works best
- GBodyForum: G-body LS swap info
- Holley/Hooker 12644HKR G-body transmission crossmember
- Strange Engineering rear end application guide
- Chevy Hardcore: Dakota Digital ECD-100 speedometer drive
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