This 1984 Airstream 310 RV originally came with a Chevy 454 ci big-block V8 and 3L80HD three-speed automatic transmission. The powertrain worked fine but the owner didn’t enjoy how loud it was and the high RPM while highway cruising. He originally was going to use a Duramax V8 but decided to go with a Vortec 8100 after realizing it would directly bolt to the existing mounts and exhaust. The 8.1 L Vortec V8 was pulled from a 2002 Chevy Silverado 2500HD truck that was purchased for $5K. The only modification needed to fit the engine was notching a small piece out of the frame for AC compressor. To lower the engine’s RPM an Allison overdrive five-speed automatic transmission was installed behind it. Follow the project’s progress here.
Source: LS1Tech (build thread)