Sucks, same thing (more or less) happened to me the same day I installed my header. Traveling home about 60mph on the interstate, then rumble rumble rumble - no power. Ended up the bearings ate the fire out of my crank...and I had just done the head swap...so there went another HUGE chunk of change and a long down time, but now I'm kinda glad it happened.
Good luck with the repair/rebuild
