Mac

Im wondering about how much horsepower or torque a stock 700r4 can handle, mines a rebuild with about 5k on it. My motor that I just droped in produced about 300 horsepower at the rear wheels, and i occasionally spray a 150 shot of nos on it. I was wondering if theres any strong 700r4s out there you can buy, because I want to buy a higher stahl converter than I have in there now, and want a shift kit but dont want to spend all the cash on these and have the trans give out. I was thinking about a hughes transmission with a vigilante conterter and a transgo transpak. Everyone keeps on telln me to drop a th350 becasue they can handle about 900 hp, but I dont want to give up my overdrive cause I drive around town alot and i have 4.10 gears. Ive heard you can get an overdrive aded to a th350 or 400 is this true, and if so how much would it cost? Just looking for my possibilitys and some help! Thanks in advance