The blower has a few screws attaching it underneath. Then it drops down from the heater core box, if it is original.
On my truck with a later V8, I have to loosen the box the heater core is in for more wiggle room.
Here are some photos:
04/19/2017 – heater core replacementCheck the captions on the photos.
Also, look for a link to an earlier replacement for more pictures.
Look for a link to Burgies page about this too.
Good luck.