Where's the Wow?

If the engine all checks out, converter health and stall speed is suspect. Was the converter new or previously used? Was the stall speed selected based on engine peak torque rpm? Have you run a stall test on the converter? If the overrunning (stator) clutch slips there won't be any torque multiplication. Result, the car will come off the line like a slug but will come alive (if the engine is OK) around 3500 to 4500 rpm.

Here's a good primer on converter function: Precision Industries

and a discussion on the stator clutch: Overrunning One Way Stator Clutch | Torque Converter

Had this problem with my 340 and a new converter with the proper stall speed turned it into a whole new experience!