Chevrolet Repair: 4.3 motor interchange

Question
I am wanting to know if a 4.3 motor from a 1999 Silverado 1500 will fit in a 2003 Silverado 1500 that currently has a 4.3 in it without any problems. Will it just drop right in there or will there.be alot of changing things that will have to be done. If so, what would that be

Answer
HI JORDAN,,AS FAR AS WILL IT FIT..YES SIR,, IT WILL DROP RIGHT IN..BUT NOW COMES THE FUN..LOTS OF UPDATES. NEW HARNESS,SENSORS COMPUTER CHANGES AND ON AND ON..YOU COULD STRIP THE OLD MOTOR AND INSTALL EVERYTHING IN THE NEW MOTOR AND HOPE THAT IT INTERCHANGES.. YOUR LOCAL BONE YARD WOULD KNOW THIS...I KNOW THIS IS NOT A LOT OF HELP BUT I DO NOT HAVE THIS INFO AT MY FINGER TIPS LIKE THE BONE YARDS DO...BUT THE ENG WILL FIT AND WORK WITH SOME CHANGE OVERS..GOOD LUCK TO YOU,,TOM..