Recently bought a 2001 4.3 vortec motor that came out of a chevy s10 blazer. I am putting it in my 1999 s10 blazer, but noticed the knock sensor's are different in thread size and also the 1999 has 1 wire and the 2001 has 2 wires. Can this problem be fixed?

 

Drill/tap the block out to 1/4" NPT. This will allow you to use the older style knock sensor.