Could be the neutral safety switch is not properly installed or connected. Look for a wired switch plug terminal that may not be connected.
How do you know that it is your car?
It wont start
Could be the relay or bad battery cable connection at the battery or relay.
Your car wont start. lol
use jumpers
What have you welded ?
how does it stall if it wont start?
Only if you can un-rebuild the car. Once a car is rebuilt, it is rebuilt forever.
Don’t no
car wont start
Once a car is rebuilt, it is rebuilt forever
catalytic converter?