Your setup sounds alot like my combination...except for I'm running a built AOD. I was told my 4200 nonlockup converter will stall to around 5000 when I launch on a 150 shot...a bit higher with even more nitrous.
Xtreme 8.5" -Heads up 1/8th mile limited 8.5 class at Kilkare Dragway
Dedpedal Racing;Sponsered by Lasota Racing
;Tuned by S&M motorsports
Boss block 338/OTB TFS HP's/SR/BW S476R/A2W/PG/FAST xfi on E85
5.57 at 128 on 26x8.5 in 1/8th, 8.81 at 157.9 w/ 1.36 60' on 275/60DR @ 3300#