727 in reverse&forward at same time in drive

So i am building a 71 dart, was a slant 6 car. I did a moderate build on the motor, 360/727. The motor runs great... I put a Transgo TF-1 kit in trans. And a Hughes 2000 stall. When i went to go on first test drive i discovered that in forward gears, the car seem "locked" will not move, however reverse seems to work. I am sure it was a error in the valve body work i did i am just wondering if anyone has some thoughts for me...Thank you very much.

Chris.