Before I make a mistake please help new mopar fan!!

Welcome to the site, You will have the same problems if not more with a 413 vs a 440 as for headers in your car. They are both RB (raised block) engines and the 383 is a B engine. Any big block engine in an a body will cost more for the conversion parts than a small block, how much money, skill, and patience do you have? It's a pretty straight forward conversion these days with the Shumacher kits sold, but it still costs a lot and is a bit of work. Unless of course, you find all of the parts you need for cheap used.
Good luck and keep us posted on what you decide to do.
How about some pics of your car?