Few questions about C6

Hey guys I'm new to the whole tranny troubleshooting and repair so I have a few questions.
First the C6 I have is mounted behind a stock 429 in a 72 F250. I noticed that when I try to come to a stop the truck tries to keep chugging forward a few times until I reach a. Complete stop then feels fine. Is this a sign of clutches going out?
Second, what is the limit in no the input shaft can take before I need to upgrade to bullet?
Third,, can someone give me the sun down on what a stall converter means and the different rpm stall converters and what they do and used for?
Fourth, what's the best kit to rebuild my tranny so it's a little beefier than stock?
Sorry for all the question all at once. Thanks.

Not sure on first question.
2 I'm over 1000 ft/lbs of torque and on the stock shaft.
3 Stall is how much rpm the converter will allow the engine to achieve. ie a 2500 stall converter will approximately let the engine rev to 2500rpm when in gear and brakes applied.
4 You aren't going to need much better.