Who installed the engine? If you were not a part of this, there could be a lot of things. If you know nothing on the installation, my first step woud be to break the ignition switch harness connection at the base of the steering column, and use a V.O.M. meter to look for continuity from one of the pins to ground. Check the end of the connection to the dash wiring first, as if the steering column was not removed, the trouble should not be on that end.I would think that maybe one of the wires to the starter may have not been routed and got against the exhaust and cooked through the insulstion, (just one possibility). Was it showing any signs of electrical trouble before the engine job?
Good luck.

"IF YOU'RE UNDER CONTROL, YOU AIN'T GOING FAST ENOUGH."