Keep the blower small (6-71 maybe). Definitely a cam change designed for your application. Head swap for breathing purposes (a bit more exhaust to evacuate). Siamesed bores on the 400 block will be a strength for you and if you already have adequate cooling, there should be no problems. Remember the camshaft centerlines and the overlap for a blown engine is dramatically different from naturaul aspiration. Crankshafts were known for breaking into two peices with the cast OEM 400 setup, be weary of what you wanna do until you know for sure which it is. And no matter which heads you run, please match the steam holes in the head for a stock block setup. Hope this helps.