I'm not talking about M52/S52 engines into E30's (been done hundreds of times) or even S14 into a 2002 (that's been done too). No, I'm talking about cars from MY car's era or older, receiving a drivetrain that features engine technology from the past five years or newer. I've been doing some research, and some of the newer engines that have come out in the last five years put out as much as 33 percent more power, along with a significant increase in fuel economy, not to mention lower emissions and a better tolerance for the more widespread use of ethanol. I should also point out that some of the engines I've looked at are made by companies other than BMW. I was inspired by this by a news article about a 55 Chevy that was retrofitted with a new LS3 engine that put out more power with reduced emissions than the conventional "crate" motors that usually go into these cars.