According to this website: http://www.supercars.net/cars/435.html "Dodge's normally aspired high performance 273 was rated at 235hp. The extra 40hp the D/Dart produced was basic hotrodding. Off the speedshop shelf bolt on's included Racer Brown valve springs, a Camcraft 284-degree .500" lift cam, Doug's Headers, and a Holley 4160 bolted to the stock intake. All were equipped with the A-833 4 Speed and a Hurst shifter, Weber clutch components, and an 8 3/4 Suregrip with 4.86 gears. Unavailable for this car were air conditioning and a warranty. There were no external badging or markings to note the D/Dart package over a regular Dart GT." The way to make a stock 273cu engine into this wonderful creation is to add the following items: 1) Racer Brown valve springs 2) The .500" ift, 284-degree Cam (also Racer Brown) 3) The Holley 4160 4bbl carb (and 4bbl intake since I have the 2bbl now). 4) Doug Thorsley headers tube headers 5) Low restriction air cleaner Sounds easy enough. Can you still get these, or similar, parts? Since 1966, is there a better way to turn a stock 1966 273 into a nice sleeper? I mean, who expects a 4 door family sedan to haul it when you stomp it? I don't need/want a 500hp monster, just something that has more ummph when I rebuild it at some future point in time. That's why I was facinated when I read about this 50 car special Dart production in 1966. I wish Dodge had done more of this. Also, I have a Sure-Grip 7.25" differential, any more umph, and I may blow out the rear end. I'd love to up that to the 8.75", but who can even find one these days without paying out the yin-yang?