I wouldnt be afraid of going big even though its a DD, you will get use to it. I went done this same road a long time ago. Go with a 4000

 

I have a stock 2002 WS6 with a Yank PE 4200 and full exhaust and it dropped from a 8.6@84 1/8 to a 7.9@??? untuned go with the Yank PT 4000 and never look back! this is the stall that most of the faster street DD LS1's whoop *** with! it's nowhere near is bad as you might think!