Both toolmanmike and I have an Isky E-4 solid cam in our 273's. You can listen to them under the sound bites sticky under exhaust. The E-4 is 260 duration and .425 lift, up to 625 cfm carb. Power from 2,000 to 5,500 RPM. I can get 20+ mpg cruising at 70 on the highway with the stock 500 cfm AFB.