If it’s one thing we love, it’s LS swaps. Taking any car and adding a modern powerplant makes us happy. It’s the best of both worlds as vintage styling meets contemporary power and dependability. One LS swap that has taken the internet and LS Fest by storm is David Stacy’s LS Postal truck. 

This is the first time we saw the LS Postal truck. It may look like a regular USPS vehicle, but when this baby fires up, you know something is different.

We last saw Stacy’s truck at LS Fest in 2019, and at the time, it housed a naturally aspirated 6.0-liter LS engine and a 6L90 transmission. And while that combination was retained, Stacy spiced it up a bit with an LSA supercharger and a tune from FasterProms. The new combination sounds killer, and we were excited to see what the power numbers would be. 

In the video, Jeremy Formato, owner of FasterProms, goes to work on the mail truck. After an aborted baseline pull, the guys found a problem with the spark plug wires. One of the wires was sandwiched between the dipstick tube and the exhaust manifold, which caused it to melt. With two wires replaced, the mail truck laid down a baseline. Formato quickly went back to work on the laptop, making some timing and fueling adjustments along with changes to the transmission. 

Here’s more proof that the LS will fit in just about anything and look good too.

After changing the tune, the Postal truck made 584 horsepower and 600 lb-ft of torque. This has to be a record of some sort, seriously. But Formato was not done yet as the 6l90 transmission was giving him some issues by downshifting. The truck was also a little rich on the top and could take some more timing. After they were happy with the tune, the team then removed the pump gas and replaced it with E85. The final result with all of these changes netted the LS Postal truck 633 horsepower and 588 lb-ft of torque. 

Have you ever seen a USPS truck do this? While this is not the best picture, you can definitely see some air under the front tire.

We reached out to Stacy to see how the new combination runs and if he has had a chance to hit the dragstrip. “It drives good. It’s very responsive and idles excellent now that it’s running on e85 with a flex-fuel sensor,” explained Stacy. He did take the truck to the dragstrip during a Cleetus And Cars event, but things didn’t go as planned. Stacy said, “Immediately after the launch, it pulled the wheels, and I had to get off the gas.” Unfortunately, he was not able to muster any good runs at the event. 

We’re excited to see the new combination next year and see how fast the LSA-powered LS Postal truck is. Don’t you wish all of the US Postal service trucks were this cool? We sure do…