I have a 1997 chevy blazer with 4.3 two wheel drive automatic. Can I put it in a 1998 chevy blazer 4.3 four wheel drive automatic?

 

Physically, there should be very few differences, none that would prohibit the installation. You will want to swap over the oil pan from the the original engine onto the donor. And just look over everything closely when you have both out.

One known difference lies in the ECT (engine coolant temperature) sensor. The 97 has two sensors, one in the head adn one near the thermostat housing. The '98 engine has only one sensor in the head.

And please be patient. Do not post your question multiple times in multiple different forum sections.