Tranny Recommendations for 600 HP

Hi everyone. I'm having my engine built now to 550 to 600 horse. I have a standard 727 tranny. Any recommendations on a rebuild, if I need it, or what I really need to get done to ensure it handles the extra horse. I was told I need a converter with 3000 stall based on my 3.91 gear set up. Any advice I can get on parts I need or suitable rebuild would be greatly appreciated!