I bought a rolled, 2003 ford ranger 4x4 4.0 liter and swapped the cab out with a 2000 2 wheel drive that had a 3.0 motor. Now it won’t start, the anti theft light is blinking and when it turns over it blows the anti theft fuse. Any ideas? Will I need to change everything out inside the dash to get it to match up?

 

First you need to find out why the fuse is blowing. Suggest you recheck all your work for a wire that may be pinched and grounded resulting in a shorted circuit.
The blinking anti-theft lamp suggests a problem with the security system. Could be the key, computer programming or both. If the computers were changed you might require the computer to be programmed to the vehicle. A capable ,certified locksmith can usually handle this. Check around and see if you can find one in your area..