I have a 1990 caprice which I recently had the 700r4 rebuilt and and when i shift into gear the car stalls out and my brake lights don't work. The car has tbi and I replaced iac already and fuel pump I been told that it maybe wiring in valve body and I really clueless

 

You probably have a wiring issue causing the torque converter clutch to engage. Check the polarity on the TCC switch, TCC solenoid, and 4-3 switch. Depending upon the year and parts used they may be either normally open or closed. You need to figure out what was used and get the appropriate wiring diagram. The good news is this can be repaired with the transmission in the car without needing any parts. You just need to properly reconnect or repin the harness as necessary.

Brake lights are a separate issue.