In 1994, as it had for a long time, the Indianapolis 500 had different engine regulations than for the rest of the CART series, ostensibly to encourage US manufacturers to enter and compete against the domination of British-built engines such as the Ilmor and Cosworth. These regulations allowed for 3.43 litre two valve pushrod engines, as well as CART's 2.65 litre four valve overhead cam engines. These 3.43 litre engines were largely production based. Ilmor saw an opening to build a motor specifically to win Indy under these regulations, by taking the pushrod regulations and building a racing engine. That engine, badged as a Mercedes, was placed in the Penske chassis, and saw Emerson Fittipaldi, Al Unser Jr and Paul Tracy dominate the 1994 Indy 500, with Little Al giving Mercedes its first modern Indy 500 win.
http://atlasf1.autosport.com/2001/jan03/jones.html
Horsepower: 800 @ 9,800 RPM
Technically it was a pushrod engine, but the cams were high on the heads and the pushrods were very short to minimize the valvetrain mass.
If you watched "Days of Thunder", that movie did a horrible disservice to NASCAR. The cars are designed with CAD/CAM and the chassis are constructed on jigs. Yes, the rules are very restrictive on technology, but with what the teams have to work with, it's as good as anyone. Despite having to utilize pushrod valvetrains on a two valve head and traditional V-8 OHV architecture, the valvetrain technology is right up there.