help with 73 340

400 horsepower ia doable but you need to go thru the engine. As far as daily drivien, you could do it on the manifolds but it's easier (read as cheaper/better) to run them. Your '73 may not have had the 8 3/4. I've seen the 8 1/4s in them before and that wouldnt surprise me if you have one in it. The earlier engines are not very different. So to reach your level figure on a total rebuild, a little bit of head work, cam, intake, carb, etc. What is your realistic budget?