what converter for this stroker combo?

WE have a 71 cuda, stroke 383, i.e. 431, stealth heads, voodoo .498in .513ex lift cam, rpm intake with a 800 thunder series AVS carb and around 10.5 -1 CR. want converter should we run? also what would be a affordable header to run with this car with out any modifying

What converter you run all depends on YOUR expectations of what it should do. Every converter is a compromise to some degree. What is the use of the car? How much rear gear do you have, and how much slippage are you willing to live with? How much cam is in the motor? It all effects the choice. Your best bet is to study up on the K factor, and if you are going to pick a shelf converter, then that may give you an idea of what you will get, if you have accurate torque info. If this is a race only deal, then loose is better than tight, and will give better consistency for brackets. About 1200 rpm stall below the expected shift points is often close. I have a 6500 stall, and shift at 7100, but it is all race, and brackets. For a street strip deal, you at least want enough stall to hit the torque peak, or very close. For a street only, then a stall close to where the cam "comes on" strong, and the torque is getting close to the numbers at peak will work well as aa compromise. As to Converter companys, I like Frank Lupos Dynamic converters. Not cheap, but they are great. There are fans of A-1, and others. I had bad luck with TCI and did not get what I paid for years ago, and have a good memory. If you have a moderate cam, a very cheap alternative may be a stock high stall that was used behind the 340 and Hemi motors. Be aware that they are a stock converter, but will stall your deal better than a stock 440 converter would. They also don't last well behind BIG motors, and I sure wouldn't use one behind a transbrake!
For the ultimate, send all your specs to a reputable company, and have one custom built. That is the best route, and you will be better off in the long run.