440 what am I missing here?

so I built a motor home 440. Did it the right way as far as I am concerned. Have a good friend that is an engine builder. Been doing it for 20 years. We stripped it down took it to my local machine shop,and had it cleaned bored 40 over,and all the parts balanced. I used an eagle crank, forged pistons, and used the 240 powerport trickflow top end kit. We topped it off with fitech fuel injection and slapped it onto a b&m street strip torqueflight pushing the power into a 8 3/4 rear-end with 3:55 Yukon gears,and Eaton trutrac. So according to trickflow this combo should be around 620 hp. This is where the disappointment starts. The truck sounds great but just won't get up on rpms. I shouldn't be able to keep tires under it. My first thought is the torque converter. I got talked out of the 3000 stall by my builder,but after further research believe that is what I should have installed. Unfortunately I have researched it so much I have become a mechanical hypochondriac and anything seems to be a plausible issue. Any body have any ideas? I am going to swap the convertor first off just don't want to be disappointed if that doesn't do the trick.