if i get a torque converter will i need i new transmission?

 

not if you bought one for your current setup.

 

NO. Here is where to get the best converter for the 4R70W. www.tccoa.com and look for dirtydOg or call 513-535-7153. Alan makes the converters for BC-Automotive and thy are the guys who put an automatic in a 600+whp Stang because the owner did not like street driving with such a stiff clutch with the 5-speed in the January issue of MM&FF. Alan has converters for every HP range but the most popular is his 10" version which is good for 300whp. Price right now is $525. The key to his converters is they are capable of being locked in 2nd gear at WOT reducing the et's even more. Drops of .8 secs and more are common. He offers a J-mod which is like a shift kit for $75. for the parts.
The only others that would be OK would be cirlce d and PI but the PI's often are opened and they change the band material to stronger stuff. I would give Alan a acall and tell him what you are looking for. He can do a stock 11" also to a point but that would not withstand the 2nd gear lock-up if you have a lock up converter as I did not check to see what year car you have. mark
PS: If you call Alan pleae tell him Mark Sweet recommended him.