Trans stock? Tune stock? How many miles?
Most feel very "loose" on 1-2 shift when stock. A tune will help a lot, but if you want to build it, make sure you research it and get the good parts. Contact Greg "TWO-TONS-OF-FUN" for the list of parts he used, or contact FLT or RPM and get what you need.
If built properly, these transmissions can hold a lot of power.